Non-ferroelectric high dielectric and preparation method thereof

Abstract

Provided is a method for preparing a grain boundary insulation-type dielectric. The method includes the steps of obtaining a titanic acid compound and a ferroelectric having a value less than a melting point of the titanic acid compound; obtaining a mixture by adding the ferroelectric material to the titanic acid compound; and sintering the mixture at a temperature equal to or more than a melting point of the ferroelectric material.

Claims

1. A method for preparing a grain boundary insulation-type dielectric, the method comprising: obtaining a titanic acid compound and a ferroelectric material having a melting point less than a melting point of the titanic acid compound; obtaining a mixture by adding the ferroelectric material to the titanic acid compound; and sintering the mixture at a temperature equal to or more than a melting point of the ferroelectric material, wherein the titanic acid compound is (Sr.sub.xLa.sub.y)Ti.sub.zO.sub.3, where 0.95x0.99, 0.01y0.05, 1.00z1.01, and x+y=1, and wherein the ferroelectric material is K.sub.0.5Na.sub.0.5NbO.sub.3.

2. The method of claim 1, wherein the sintering comprises sintering under a reducing atmosphere and a subsequent heat treatment under an oxidizing atmosphere, and the subsequent heat treatment under the oxidizing atmosphere is performed under normal pressure.

3. A method of claim 1, for preparing a grain boundary insulation-type dielectric, the method comprising: obtaining a titanic acid compound and a ferroelectric material having a melting point less than a melting point of the titanic acid compound; obtaining a mixture by adding the ferroelectric material to the titanic acid compound; and sintering the mixture at a temperature equal to or more than a melting point of the ferroelectric material, wherein the titanic acid compound is (Ba.sub.xLa.sub.y)Ti.sub.zO.sub.3, where 0.95x0.99, 0.01y0.05, 1.00z1.01, and x+y=1, and wherein the ferroelectric material is K.sub.0.5Na.sub.0.5NbO.sub.3.

4. The method of claim 3, further comprising adding tetraethyl orthosilicate (TEOS) to the mixture of the titanic acid compound and the ferroelectric material.

5. The method of claim 3, further comprising subjecting the mixture to pre-heat treatment (prefiring) prior to the sintering.

6. The method of claim 3, wherein the sintering comprises sintering under a reducing atmosphere and a subsequent heat treatment under an oxidizing atmosphere, and the subsequent heat treatment under the oxidizing atmosphere is performed under a N.sub.2 atmosphere or normal pressure.

7. The method of claim 1, wherein an addition ratio of the ferroelectric material is 2 to 20 mol% based on the titanic acid compound.

8. A grain boundary insulation-type dielectric wherein a ferroelectric material, which is K.sub.0.5Na.sub.0.5NbO.sub.3, in (Sr.sub.xLa.sub.y)Ti.sub.zO.sub.3, which is a strontium titanate compound, is distributed at a grain boundary of the strontium titanate compound, where 0.95x0.99, 0.01y0.05, 1.00z1.01, and x+y=1.

9. The grain boundary insulation-type dielectric of claim 8, wherein the grain boundary insulation-type dielectric has an average particle size of 0.3 m to 1 m.

10. The grain boundary insulation-type dielectric of claim 8, wherein the grain boundary insulation-type dielectric has a relative dielectric constant of 4,500 to 6,000 and a dielectric loss of 2 to 5% in a frequency region of 1 MHz or more.

11. A grain boundary insulation-type dielectric wherein a ferroelectric material, which is K.sub.0.5Na.sub.0.5NbO.sub.3, in (Ba.sub.xLa.sub.y)Ti.sub.zO.sub.3, which is a barium titanate compound, is distributed at a grain boundary of the barium titanate compound, where 0.95x0.99, 0.01y0.05, 1.00z1.01, and x+y=1.

12. The grain boundary insulation-type dielectric of claim 11, wherein the grain boundary insulation-type dielectric has an average particle size of 0.2 m to 1m.

13. The grain boundary insulation-type dielectric of claim 11, wherein the grain boundary insulation-type dielectric has a relative dielectric constant of 1,400 to 3,200 and a dielectric loss of 10 to 20% in a frequency region of 1 MHz or more.

14. The grain boundary insulation-type dielectric of claim 11, wherein in the grain boundary insulation-type dielectric, a change width in relative dielectric constant is maintained at 0 to 20 and a change width in dielectric loss is maintained at 0 to 2%, regardless of the frequency region.

15. The grain boundary insulation-type dielectric of claim 8, wherein a ratio of the ferroelectric in the grain boundary insulation-type dielectric is 2 to 20 mol% based on the titanic acid compound.

16. The method grain boundary insulation-type dielectric of claim 11, wherein a ratio of the ferroelectric in the grain boundary insulation-type dielectric is 2 to 20 mol% based on the titanic acid compound.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings included as a part of the detailed description to assist understanding of the present invention provide exemplary embodiments of the present invention and explain the technical spirit of the present invention along with the detailed description.

(2) FIG. 1 is a flow chart explaining a method for preparing a grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention.

(3) FIG. 2 is a schematic view illustrating a sintering process of the grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention.

(4) FIG. 3 is a scanning electron microscope image illustrating particle sizes of a (Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 compound according to an exemplary embodiment of the present invention and a raw material powder.

(5) FIG. 4 is a flowchart illustrating a preparation method when a titanic acid compound is a barium titanate compound, in the grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention.

(6) FIG. 5 is a scanning electron microscope image illustrating the micro structures of the samples of (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKNN according to an exemplary embodiment of the present invention.

(7) FIG. 6 is a scanning electron microscope image of (Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 powder prepared through a calcination process according to an exemplary embodiment of the present invention.

(8) FIG. 7 is a scanning electron microscope image illustrating changes in micro structures according to the content of TEOS in 90(Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-10KNN according to an exemplary embodiment of the present invention.

(9) FIG. 8A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKNN according to the present invention, and FIG. 8B is a graph illustrating changes in dielectric loss values.

(10) FIG. 9A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKN according to the present invention, and FIG. 9B is a graph illustrating changes in dielectric loss values.

(11) FIG. 10A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)BT-xKNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of an N.sub.2 atmosphere in (100-x)BT-xKNN, and FIG. 10B is a graph illustrating changes in dielectric loss values.

(12) FIG. 11A is a graph illustrating changes in relative dielectric constant values according to the addition of TEOS in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of an N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 11B is a graph illustrating changes in dielectric loss values.

(13) FIG. 12A is a graph illustrating changes in relative dielectric constant values when (100-x)BT-xKNN is subjected to pre-heat treatment (prefiring) as a pre-step of sintering in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of an N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 12B is a graph illustrating changes in dielectric loss values.

(14) FIG. 13A is a graph illustrating changes in relative dielectric constant values of 90BT-10KNN according to the sintering temperature performed under a reducing atmosphere when a subsequent heat treatment process is performed under an N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 13B is a graph illustrating changes in dielectric loss values.

(15) FIG. 14A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)BT-xKNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 14B is a graph illustrating changes in dielectric loss values.

(16) FIG. 15A is a graph illustrating changes in relative dielectric constant values according to the addition of TEOS in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 15B is a graph illustrating changes in dielectric loss values.

(17) FIG. 16A is a graph illustrating changes in relative dielectric constant values when (100-x)BT-xKNN is subjected to pre-heat treatment (prefiring) as a pre-step of sintering in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 16B is a graph illustrating changes in dielectric loss values.

(18) FIG. 17A is a graph illustrating changes in relative dielectric constant values of 90BT-10KNN according to the sintering temperature under a reducing atmosphere when a subsequent heat treatment process is performed under normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 17B is a graph illustrating changes in dielectric loss values.

DETAILED DESCRIPTION

(19) The terms or words used in the present specification and the claims should not be construed as being limited as typical or dictionary meanings, and should be construed as meanings and concepts conforming to the technical spirit of the present invention on the basis of the principle that an inventor can appropriately define concepts of the terms in order to describe his or her own invention in the best way. Accordingly, since the exemplary embodiments described in the present specification and the configurations illustrated in the drawings are only the most preferred exemplary embodiment of the present invention and do not represent all of the technical spirit of the present invention, it is to be understood that various equivalents and modified embodiments, which may replace these exemplary embodiments and configurations, are possible at the time of filing the present application. Hereinafter, a non-ferroelectric high electric and a preparation method thereof according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

(20) FIG. 1 is a flow chart explaining a method for preparing a grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention, and FIG. 2 is a schematic view illustrating a sintering process of the grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention.

(21) Referring to FIG. 1, a method for preparing a grain boundary insulation-type dielectric will be described. A method for preparing a grain boundary insulation-type dielectric according to the present invention is characterized by including: obtaining a titanic acid compound and a ferroelectric having a value less than a melting point of the titanic acid compound (S100); obtaining a mixture by adding the ferroelectric material to the titanic acid compound (S110); and sintering the mixture at a temperature equal to or more than a melting point of the ferroelectric material (S120).

(22) Step S100 will be described. The titanic acid compound (powder) is prepared by wet-milling, drying, grinding, and sieving a raw material powder, and calcining the resulting product. A ferroelectric material has a perovskite structure having a chemical formula of ABO.sub.3, and in order to synthesize the ferroelectric material, the ferroelectric material is prepared by milling, drying, grinding, and sieving a raw material powder including A and B elements, and calcining the resulting product at a predetermined molar ratio in the same manner as in the titanic acid compound. Here, a melting point of the ferroelectric needs to be lower than that of the titanic acid compound.

(23) Step S110 is a step of mixing the prepared titanic acid compound with the prepared ferroelectric. Since a ferroelectric 200 is entirely evenly distributed in a titanic acid compound 100 during the mixing of the titanic acid compound with the ferroelectric, the ferroelectric 200 allows a titanic acid compound grain boundary to permeate into a liquid phase to form a grain boundary during the preparation of a dielectric, thereby preparing a dielectric having large sizes.

(24) Step S120 is a step of sintering a mixture of the titanic acid compound and the ferroelectric at a temperature equal to or more than a melting point of the ferroelectric material. FIG. 2(c) illustrates a state where the mixture prepared in step S110 is sintered at a temperature equal to or more than a melting point of the ferroelectric material. When the mixture is sintered at a temperature equal to or more than the melting point of the ferroelectric, the ferroelectric is melted, and thus evenly distributed among particles of the titanic acid compound 100. Preferably, as the sintering temperature, a temperature of approximately 70% to approximately 90% of the melting point of the titanic acid compound is suitable, but the sintering temperature is not limited thereto.

(25) Referring to FIG. 2, step S120 according to the present invention will be specifically described.

(26) The sintering step S120 is carried out by performing a process of sintering a mixture of the titanic acid compound 100 and the ferroelectric 200 under a reducing atmosphere and a subsequent heat treatment process under an oxidizing atmosphere.

(27) FIG. 2(a) illustrates a form in which the titanic acid compound 100 and the ferroelectric 200 are mixed through step S110. It can be confirmed that the ferroelectric 200 is entirely evenly distributed in the titanic acid compound 100.

(28) FIG. 2(b) illustrates a structure before the heat treatment temperature reaches a melting point of the ferroelectric 200 in performing sintering on the mixture of the titanic acid compound 100 and the ferroelectric 200 under a reducing atmosphere. When a sintering is performed under a reducing atmosphere, grain growth and densification of the titanic acid compound (for example, ST and BT) occur. Compared with FIG. 2(a), particles of the titanic acid compound aggregate, and as a result, the form is changed, but is not yet a completely densified form, so that it can be confirmed that empty spaces among the titanic acid compound particles are present. The ferroelectric 200 is present in the empty space. As the densification occurs, the empty spaces begin to be filled.

(29) FIG. 2(c) illustrates a structure after the sintering temperature under a reducing atmosphere reaches the melting point of the ferroelectric 200.

(30) As the heat treatment temperature passes through the melting point of the ferroelectric, the phase of the ferroelectric is changed from the solid phase to the liquid phase, and the ferroelectric flows into the grain boundary. In this case, grain growth and densification of the titanic acid compound (for example, ST and BT) actively occur, and simultaneously, the ferroelectric 200 in a liquid state is present at the grain boundary.

(31) FIG. 2(d) illustrates a structure after the sintering under a reducing atmosphere is finished. When the temperature is lowered as the heat treatment is finished, that is, when the temperature is lowered to a temperature equal to or less than a melting point of the ferroelectric 200, the ferroelectric 200 in a liquid state present at the grain boundary is changed into a solid state.

(32) FIG. 2(e) illustrates a structure after the subsequent heat treatment is performed under an oxidizing atmosphere. The reactions of Defect Chemical Formulae 3 and 4 mentioned below at the grain boundary occur, and as a result, the insulation property of the grain boundary is reinforced.

(33) Meanwhile, the heat treatment step may be performed by lowering the sample to a room temperature state after the sintering under a reducing atmosphere, creating an atmosphere as an oxidizing atmosphere of a subsequent heat treatment at room temperature, and then increasing the temperature to the temperature of the subsequent heat treatment. However, after the sintering under a reducing atmosphere, the subsequent heat treatment may be performed by lowering the temperature to the subsequent heat treatment temperature, which is not in a room temperature state, and changing the atmosphere into the oxidizing atmosphere. In the case of the former, the ferroelectric in a liquid phase is changed into a solid phase when the temperature is lowered to room temperature after the completion of the sintering under a reducing atmosphere, and in the case of the latter, the ferroelectric in a liquid phase is changed into a solid phase when the temperature is lowered to the subsequent heat treatment temperature after the sintering under a reducing atmosphere.

(34) The subsequent heat treatment may be performed at a temperature equal to or less than the melting point of the ferroelectric, and if the subsequent heat treatment is performed at a temperature equal to or more than the melting point, the ferroelectric at the grain boundary is present in a liquid phase even during the subsequent heat treatment, and is changed into a solid phase when the temperature is decreased to room temperature after the completion of the subsequent heat treatment.

(35) As described above, for a titanic acid solid solution by the present invention, the process procedure is relatively simple because a two-step heat treatment process under a reducing atmosphere and under an oxidizing atmosphere is performed unlike existing methods of performing sintering on a power molded body, applying oxide to the powder molded body, and performing a heat treatment.

(36) A principle in which a grain boundary insulation-type dielectric is formed through the sintering under a reducing atmosphere and the subsequent heat treatment under an oxidizing atmosphere will be specifically described by exemplifying a strontium titanate compound. A donor to be described in the present invention is a material having a valence larger than that of an element at a site to be added, and the donor may be added by substituting a strontium (Sr) site with lanthanum (La) or substituting the strontium (Sr) site with an element having a valence of 3 or more, which corresponds to lanthanum (La).

(37) When a donor having a large valence substitutes the original atomic position, a positive charge is formed. In this case, an infiltration-type oxygen ion, a positive ion vacancy, or an electron is additionally formed and offsets a positive charge, and electrical neutrality is maintained.

(38) Since it is difficult for an oxygen ion having a large ion size to enter the lattices, the infiltration-type oxygen ion is minimally formed, and when a heat treatment is performed at normal pressure in which an oxygen partial pressure is high, a positive ion vacancy is formed, and as the oxygen partial pressure is lowered, an electron rather than the positive ion vacancy is formed, thereby maintaining the electrical neutrality.

(39) When the donor is added, the system is classified into three regions according to the oxygen partial pressure. The case where the oxygen partial pressure is very low, the case where the oxygen pressure is low, and the case where the oxygen partial pressure is high are shown in Defect Chemical Formulae 1 to 3, respectively in accordance with a Kroger-Vink notation method. V indicates a vacancy, the subscript and the superscript indicate an atom and an effective charge originally positioned at a site to be substituted, respectively, indicates a positive effective charge, and indicates a negative effective charge.

(40) Defect Chemical Formula 1 is a case where the oxygen partial pressure is very lowas in a H.sub.2 atmosphere, the electric conductivity is almost regardless of the concentration of a donor added, and as the oxygen partial pressure is increased, the electric conductivity is decreased.

(41) $\begin{array}{cc}{O}_0->\frac{1}{2}{O}_2+V_O^{**}+2e^{}& \left(\mathrm{Defect}\mathrm{Chemical}\mathrm{Formula}1\right)\end{array}$

(42) When the oxygen partial pressure is low as in a 95N.sub.2-5H.sub.2 or nitrogen atmosphere, and the like, the electric conductivity is almost regardless of the oxygen partial pressure, and since a donor additive forms free electrons according to Defect Chemical Formula 2, the electric conductivity is increased by the concentration of the additive.

(43) $\begin{array}{cc}{\mathrm{Lo}}_2{O}_3\left(-2\mathrm{SrO}\right)->2{\mathrm{La}}_{\mathrm{Sr}}^{*}+2O_O+\frac{1}{2}{O}_2+2e^{}{\mathrm{Nb}}_2{O}_5\left(-2{\mathrm{Ti}O}_2\right)->2{\mathrm{Nb}}_{\mathrm{Ti}}^{*}+4O_O+\frac{1}{2}{O}_2+2e^{}& \left(\mathrm{Defect}\mathrm{Chemical}\mathrm{Formula}2\right)\end{array}$

(44) When the oxidizing atmosphere, that is, the oxygen partial pressure (Po.sub.2) is high, strontium ion vacancies are formed according to Defect Chemical Formula 3, so that since free electrons are not formed and the electric charges are compensated by ions to achieve the electrical neutrality, the electric conductivity is decreased.

(45) $\begin{array}{cc}{\mathrm{Lo}}_2{O}_3\left(-3\mathrm{SrO}\right)->2{\mathrm{La}}_{\mathrm{Sr}}^{*}+V_{\mathrm{Sr}}^{}+3O_{o}2{\mathrm{Nb}}_2{O}_5\left(-5{\mathrm{Ti}O}_2\right)->4{\mathrm{Nb}}_{\mathrm{Ti}}^{*}+V_{\mathrm{Ti}}^{}+10O_o& \left(\mathrm{Defect}\mathrm{Chemical}\mathrm{Formula}3\right)\\ \frac{1}{2}{O}_2+V_O^{**}+2e^{}->O_O& \left(\mathrm{Defect}\mathrm{Chemical}\mathrm{Formula}4\right)\end{array}$

(46) When the oxygen partial pressure is increased, oxygen in the atmosphere diffuses into the sintered body, and as a result, a reaction occurs in a right direction where an oxygen vacancy and an electron meet together, and since oxygen diffuses more rapidly at the grain boundary than in the grain, when a heat treatment is performed under an oxidizing atmosphere, an oxidation layer is formed only at the grain boundary and the resistance is increased. After the donor is added, a semiconducting sintered body is obtained by sintering under a reducing atmosphere (Defect Chemical Formulae 1 and 2), and then an insulating grain boundary is created by forming an oxidation layer only at the grain boundary (Defect Chemical Formulae 3 and 4)through a short subsequent heat treatment under an oxidizing atmosphere. Through sintering under a reducing atmosphere and a subsequent heat treatment process under an oxidizing atmosphere, a grain boundary insulation-type capacitor consisting of semiconducting particles and insulating grain boundaries may be prepared. Hereinafter, a process of performing each step will be described in detail through the examples.

(47) FIG. 3 is a scanning electron microscope image illustrating particle sizes of a (Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 compound according to an exemplary embodiment of the present invention and a raw material powder.

(48) A titanic acid compound (powder) and a ferroelectric powder are prepared by each calcining SrCO.sub.3, La.sub.2O.sub.3, TiO.sub.2 and KCO.sub.3, NaCO.sub.3, and Nb.sub.2O.sub.5 raw material powders. As illustrated in FIG. 3, (Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 may be prepared by calcining La.sub.2O.sub.3 and TiO.sub.2 powders. Hereinafter, (Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 is indicated by ST, (Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 is indicated by BT, (K.sub.0.5Na.sub.0.5)NbO.sub.3 is indicated by KNN, and KNbO.sub.3 is indicated by KN.

(49) A method for preparing a high dielectric will be specifically described by exemplifying a case where the titanic acid compound is a strontium titanate compound. A high dielectric consisting of a strontium titanate compound is added in an amount of 1 to 5 mol % based on a site in which a donor additive acts as a donor, and contains a titanium (Ti) site at a molar ratio of 1.00 to 1.01 based on the strontium (Sr) site. After sintering is performed under a reducing atmosphere for 1 to 2 hours by adding a ferroelectric having a melting point equal to or less than the sintering temperature of the present compound in an amount of 2 to 20 mol % based on a strontium titanate (SrTiO.sub.3) solid solution and mixing the strontium titanate (SrTiO.sub.3) solid solution, a subsequent heat treatment is performed under an oxidizing atmosphere for 30 minutes to 1 hour.

(50) In a donor, lanthanum (La) is added to a strontium (Sr) site or niobium (Nb) is added to a titanium (Ti) site, and the element is added in an amount of 1 to 5 mol % based on a position to be added. When the addition concentration is less than 1 mol %, semiconducting particles are not formed during sintering under a reducing atmosphere, and when the addition concentration is more than 5 mol %, the element added as the donor may be precipitated at the grain boundary, so that an addition concentration of 1 to 5 mol % is appropriate.

(51) A ferroelectric having a melting point equal to or less than the sintering temperature of the present compound is melted during the sintering process of the compound, and thus enters between particles. When cooled after the sintering, the ferroelectric material remains at the grain boundary as it is, and thus, acts as an insulator in a grain boundary insulation-type capacitor model, thereby increasing the apparent dielectric constant of the grain boundary.

(52) The ferroelectric having a melting point equal to or less than the sintering temperature of the present compound is ABO.sub.3, where A.sup.+=K, Na, K.sub.0.5Na.sub.0.5 or a mixture thereof and B.sup.5+=Nb or Ta. Each melting point of KNbO.sub.3, KTaO.sub.3, NaNbO.sub.3, NbTaO.sub.3 and K.sub.0.5Na.sub.0.5NbO.sub.3 is 1,039 C., 1,370 C., 1412 C., 1780 C., and 1140 C. to 1420 C., respectively [F. S. Galasso, Perovskite and High Tc Superconductors, p. 176 Gordon and Breach Science Publishers, New York (1986); B. Jaffe, Piezoelectric Ceramics; Academic Press: London, UK (1971)]. Accordingly, it is preferred that a ferroelectric added to the strontium titanate-based solid solution is KNbO.sub.3, KTaO.sub.3, NaTaO.sub.3, or K.sub.0.5Na.sub.0.5NbO.sub.3.

(53) When the aforementioned ferroelectric is mixed with a strontium-based solid solution, in the case where the ferroelectric is present in an amount of less than 2 mol % based on the strontium-based solid solution, it is difficult for the ferroelectric to be uniformly present at all the grain boundaries during the sintering, and in the case where the ferroelectric is added in an amount of 20 mol % or more, the apparent dielectric constant (.sub.app) is rather decreased as the thickness (d.sub.gb) of the grain boundary is increased. Accordingly, the ferroelectric to be added is appropriately present in an amount of 2 to 20 mol % based on the strontium-based solid solution.

(54) FIG. 4 is a flowchart illustrating a preparation method when a titanic acid compound is a barium titanate compound, in the grain boundary insulation-type dielectric according to an exemplary embodiment of the present invention.

(55) A method for preparing a high dielectric (S200, S210, and S240) when the titanic acid compound is a barium titanate compound (BaTiO.sub.3) is similar to the aforementioned method for preparing a strontium titanate compound.

(56) However, as illustrated in FIG. 4, in the case of a high dielectric based on a barium titanate compound, a step of adding TEOS to a ferroelectric material and a titanic acid compound (S220) and a step of subjecting a mixture to which the TEOS is added to pre-heat treatment (prefiring) S230 may be additionally performed. Meanwhile, barium titanate is similar to the case of strontium titanate, and the donor may be added by substituting a barium (Ba) site with lanthanum (La) or substituting the barium (Ba) site with an element having a valence of 3 or more, which corresponds to lanthanum (La).

(57) The difference between detailed process conditions of barium titanate and strontium titanate will be described through the Examples described below.

(58) The present invention will be specifically described through the following Examples. However, the following Examples are provided for illustrative purposes only, and are not intended to limit the technical scope of the present invention.

EXAMPLE 1

(59) In Example 1 according to the present invention, a dielectric having a composition of (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKN (x=2, 5, 10, 15, and 20) was prepared.

(60) Raw material powders used to prepare these dielectrics are SrCO.sub.3, La.sub.2O.sub.3, TiO.sub.2, KCO.sub.3, and Nb.sub.2O.sub.5. TiO.sub.2 was allowed to have an average particle size of several hundred nanometers after all the processes were completed by using a powder having a size of several tens of nanometers. La.sub.2O.sub.3 was used as a donor additive, and KCO.sub.3 and Nb.sub.2O.sub.5 were separately synthesized and allowed to be positioned at the grain boundary during the sintering process of strontium titanate to which the donor was added.

(61) First, lanthanum (La) was positioned at an Sr site to act as a donor, and Sr, La, and Ti were put into a polyethylene bottle at a molar ratio of Sr:La:Ti=0.95:0.05:1.01 in order to slightly exceed Ti, and the resulting mixture was wet-milled with ZrO.sub.2 balls for 24 hours by using an alcohol solvent. After the product was dried on a hot plate until the slurry state was reached, the dried product was completely dried in an oven at 80 C., ground in an agate mortar, and then sieved.

(62) When the melting point is lower than that of a strontium titanate compound, K and Nb at a molar ratio of K:Nb=1:1 were milled, dried, ground, and sieved in the same manner as in the above-described method in order to synthesize a ferroelectric KNbO.sub.3 having a perovskite structure.

(63) A strontium titanate raw material mixed powder to which lanthanum (La) was added and a KNbO.sub.3 raw material mixed powder were calcined at 1,300 C. for 4 hours and at 850 C. for 4 hours, respectively, by using an electric furnace in the form of a box. Preferably, the raw material mixture of strontium titanate may be calcined at 1,250 to 1,300 C., and the KNbO.sub.3 raw material mixed powder may be calcined at 800 to 900 C.

(64) KNbO.sub.3 was added at a molar ratio of 0, 5, 10, 15, and 20:1 to the synthesized strontium titanate-based powder, and the resulting mixture was put into a polyethylene bottle and wet-milled with zirconia (ZrO.sub.2) balls for 24 hours by using an alcohol solvent. The resulting product was milled, dried, ground, and sieved in the same manner as in the above-described method. In order to manufacture a grain boundary insulation-type capacitor, a synthesized powder was injected into a metal mold having a diameter of 12 mm, primarily molded, and isostatically molded at 200 MPa for 5 minutes (preferably 5 to 10 minutes).

(65) Highly dense semiconducting particles were prepared by sintering the prepared molded body at 1,450 C. under a nitrogen atmosphere in a vertical tube furnace for 2 hours. Thereafter, the grain boundary was oxidized by performing a subsequent heat treatment under conditions of 1,200 C., normal pressure, and 30 minutes in the vertical tube furnace, and a grain boundary insulation-type capacitor was prepared. Preferably, the heat treatment under the reducing atmosphere may be performed at 1,300 to 1,500 C., and the heat treatment under the oxidizing atmosphere may be performed at 1,100 to 1,200 C.

EXAMPLE 2

(66) In Example 2 according to the present invention, a dielectric having a composition of (100-x)ST-xKNN (x=2, 5, 10, 15, and 20) was prepared.

(67) Raw material powders used to prepare these dielectrics are SrCO.sub.3, La.sub.2O.sub.3, TiO.sub.2, KCO.sub.3, NaCO.sub.3, and Nb.sub.2O.sub.5, and TiO.sub.2 was allowed to have an average particle size of several hundred nanometers after all the processes were completed by using a powder having a size of several decade nanometers.

(68) First, Sr, La, and Ti were put into a polyethylene bottle at a molar ratio of Sr:La:Ti=0.95:0.05:1.01 in order to slightly exceed Ti, and the resulting mixture was wet-milled with zirconia (ZrO.sub.2) balls for 24 hours by using an alcohol solvent. After the product was dried on a hot plate until the slurry state was reached, the dried product was completely dried in an oven at 80 C., ground in an agate mortar, and then sieved. K and Nb at a molar ratio of K:Nb=1:1 were milled, dried, ground, and sieved in the same manner as in the above-described method in order to synthesize K.sub.0.5Na.sub.0.5NbO.sub.3.

(69) A strontium titanate raw material mixed powder to which lanthanum (La) was added and a K.sub.0.5Na.sub.0.5NbO.sub.3 raw material mixed powder were calcined at 1,300 C. for 4 hours and at 900 C. for 4 hours, respectively, by using an electric furnace in the form of a box. Preferably, the raw material mixture of strontium titanate may be calcined at 1,250 to 1,300 C., and the K.sub.0.5Na.sub.0.5NbO.sub.3 raw material mixed powder may be calcined at 800 to 900 C.

(70) K.sub.0.5Na.sub.0.5NbO.sub.3 was added at a molar ratio of 0, 5, 10, 15, and 20:1 to the synthesized strontium titanate-based powder, and the resulting mixture was put into a polyethylene bottle and wet-milled with zirconia (ZrO.sub.2) balls for 24 hours by using an alcohol solvent. The resulting product was milled, dried, ground, and sieved in the same manner as in the above-described method. In order to manufacture a grain boundary insulation-type capacitor, a synthesized powder was injected into a metal mold having a diameter of 12 mm, primarily molded, and isostatically molded at 200 MPa for 5 minutes.

(71) Highly dense semiconducting particles were prepared by sintering the prepared molded body at 1,450 C. under a nitrogen atmosphere in a vertical tube furnace for 2 hours. Thereafter, a grain boundary insulation-type capacitor was prepared by oxidizing the grain boundary through a subsequent heat treatment at 1,200 C. and normal pressure for 30 minutes in the vertical tube furnace. Preferably, the heat treatment under the reducing atmosphere may be performed at 1,300 to 1,500 C., and the heat treatment under the oxidizing atmosphere may be performed at 1,100 to 1,200 C.

(72) FIG. 5 is a scanning electron microscope image illustrating the micro structures of the samples of (100-x)ST-xKNN according to an exemplary embodiment of the present invention. The sintering under the reducing atmosphere and the subsequent heat treatment under the oxidizing atmosphere were performed under conditions of 1,450 C., N.sub.2, and 2 hours and under conditions of 1,200 C., normal pressure (air), and 30 minutes, respectively.

EXAMPLE 3

(73) In Example 3 according to the present invention, a dielectric having a composition of (100-x)(Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xK.sub.0.5Na.sub.0.5NbO.sub.3 (x=2, 5, 10, 15, and 20) was prepared.

(74) Raw material powders used to prepare these dielectrics are BaCO.sub.3, La.sub.2O.sub.3, TiO.sub.2, KCO.sub.3, NaCO.sub.3, and Nb.sub.2O.sub.5, and TiO.sub.2 was allowed to have an average particle size of several hundred nanometers after all the processes were completed by using a powder having a size of several decade nanometers.

(75) First, Ba, La, and Ti were put into a polyethylene bottle at a molar ratio of Sr:La:Ti=0.95:0.05:1.01, and the resulting mixture was wet-milled with zirconia (ZrO.sub.2) balls for 24 hours by using an alcohol solvent. After the product was dried on a hot plate until the slurry state was reached, the dried product was completely dried in an oven at 80 C., ground in an agate mortar, and then sieved. K and Nb at a molar ratio of K:Nb=1:1 were milled, dried, ground, and sieved in the same manner as in the above-described method in order to synthesize K.sub.0.5Na.sub.0.5NbO.sub.3.

(76) A barium titanate raw material mixed powder to which lanthanum (La) was added and a K.sub.0.5Na.sub.0.5NbO.sub.3 raw material mixed powder were calcined at 1,100 C. for 4 hours and at 900 C. for 4 hours, respectively by using an electric furnace in the form of a box.

(77) K.sub.0.5Na.sub.0.5NbO.sub.3 was added at a molar ratio of 0, 5, 10, 15, and 20:1 to the synthesized strontium titanate-based powder, 0 to 8 wt % of tetra-ethyl ortho silicate (TEOS) was added thereto, the resulting mixture was put into a polyethylene bottle and wet-milled with ZrO.sub.2 balls for 24 hours by using an alcohol solvent, and the resulting product was milled, dried, ground, and sieved in the same manner as in the above-described method. When 0.5 to 8 wt % of TEOS is added thereto, dielectric characteristics may be improved. In order to manufacture a grain boundary insulation-type capacitor, a synthesized powder was injected into a metal mold having a diameter of 12 mm, primarily molded, and isostatically molded at 200 MPa for 5 minutes.

(78) A molded body prepared prior to the sintering was subjected to a pre-heat treatment (prefiring) process maintained under a 5H.sub.2-95N.sub.2 atmosphere (reducing atmosphere) at 900 C. for 5 hours in a vertical tube furnace. By performing a pre-heat treatment (prefiring) prior to the sintering, the density of the high dielectric may be increased, and a change in dielectric constant according to the frequency may be caused to occur less than before. The pre-heat treatment (prefiring) was performed under a 5H.sub.2-95N.sub.2 atmosphere, and thus may be performed under the same atmosphere as the sintering under a reducing atmosphere. It is possible to remove impurities introduced therein during the process of preparing the powder through the pre-heat treatment (prefiring).

(79) After the pre-heat treatment (prefiring), highly dense semiconducting particles were prepared by performing sintering under a 5H.sub.2-95N.sub.2 atmosphere (reducing atmosphere) at 1,200 to 1,280 C. for 2 hours. Thereafter, a capacitor was prepared by oxidizing the grain boundary through a subsequent heat treatment at 1,000 to 1,100 C. under N.sub.2 or normal pressure (both under an oxidizing atmosphere) in a vertical tube furnace for 30 minutes. In the heat treatment temperature and atmosphere, a desired reaction did not occur out of the temperature range, so that it was experimentally confirmed that in the prepared dielectric, dielectric characteristics and mechanical characteristics significantly deteriorated.

(80) In the case of (Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3, both N.sub.2 and normal pressure are under an oxidizing atmosphere, but the difference in dielectric characteristics was exhibited due to the difference in degree of oxidation. When the heat treatment was performed under N.sub.2, a high dielectric constant (high relative dielectric constant or high dielectric constant) was exhibited, whereas when the heat treatment was performed under normal pressure, a stable dielectric constant and a low dielectric loss (loss tangent, tan ) were exhibited in a wide frequency region of 100 Hz to 1 MHz.

(81) FIG. 6 is a scanning electron microscope image of (Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3 powder prepared through a calcination process according to an exemplary embodiment of the present invention, and FIG. 7 is a scanning electron microscope image illustrating changes in micro structures according to the content of TEOS in 90(Ba.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-10KNN. The sintering under the reducing atmosphere and the subsequent heat treatment under the oxidizing atmosphere were performed under conditions of 1,200 C., 5H.sub.2-95N.sub.2, and 2 hours and under conditions of 1,100 C., normal pressure (air), and 30 minutes, respectively.

Analysis Example

(82) After a cross-section of the strontium titanate compound prepared in Example 1 was cut, the compound was sequentially polished by using 6 m, 3 m, and 1 m diamond suspensions. Thereafter, thermal etching was performed at 1,000 to 1,100 C. in a vertical tube furnace for 1 minute, and then quenching was performed under air atmosphere, and in order to prevent a phenomenon in which electrons are accumulated on a surface of a sample when electrons are injected thereinto, the surface was coated with osmium (Os) and observed by a scanning electronic microscopy.

(83) After the upper and lower surfaces of the solid solution were polished to 30 m, a silver paste (Ag paste) was applied on one surface thereof by a silk screen technique, and organic materials included in the paste were removed by drying the paste in an oven at 120 C. for 30 minutes. The same process was also repeated on the opposite surface. The relative dielectric constant and the dielectric loss were measured at 0.5 V and 100 Hz to 5.5 MHz. The average particle size was obtained by SEM, an XRD analysis was performed, and the relative dielectric constant and the dielectric loss were measured at 1 MHz.

(84) FIG. 8A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKNN according to the present invention, and FIG. 8B is a graph illustrating changes in dielectric loss values.

(85) Referring to FIGS. 8A and 8B and Table 1, it can be confirmed that even though the dielectric based on the strontium titanate compound has small particle sizes, a high relative dielectric constant and a low dielectric loss are exhibited in a high frequency region. The following Table 1 shows a relative dielectric constant and a dielectric loss of the dielectric based on strontium titanate (SrTiO.sub.3).

(86) TABLE-US-00001 TABLE 1 composition and annealing condition dielectric characteristics ferroelectric 2nd firing dielectric Dielectric loss, donor material condition grain constant, .sub.r tan [%] sample La KNN temper- atmo- size 10 100 1 10 100 1 no. [mol %] [mol %] ature sphere [m] kHz kHz MHz kHz kHz MHz 1 5 5 1200 air 0.6 5,390 4,900 4,760 28.7 6.3 2.4 2 5 10 1200 air 0.7 5,100 4,850 4,680 11.3 3.6 2.8 3 5 20 1200 air 0.7 6,126 5,625 5,532 17.7 5.0 4.5

(87) The dielectric based on the strontium titanate compound according to the present invention exhibited a high relative dielectric constant value of 4,600 or more and also exhibited a dielectric loss value of less than 5% in a particle size of 0.3 m to 1 m in a high frequency region of 1 MHz.

(88) FIG. 9A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKN according to the present invention, and FIG. 9B is a graph illustrating changes in dielectric loss values.

(89) Referring to FIG. 9, it can be confirmed that the relative dielectric constant and dielectric loss values are constantly maintained without a significant change, regardless of the frequency region. It was confirmed that numerically, the relative dielectric constant was maintained within a change width of about 0 to 10, and the dielectric loss was maintained within a change width of about 0% to 5%. Meanwhile, the particle size of the dielectric exhibited a value of 0.5 m or less.

(90) The following Table 2 shows the relative dielectric constant and dielectric loss of the (100-x)(Sr.sub.0.95La.sub.0.05)Ti.sub.1.01O.sub.3-xKN dielectric, and the like.

(91) TABLE-US-00002 TABLE 2 composition and annealing condition dielectric characteristics ferroelectric 2nd firing dielectric Dielectric loss, donor material condition grain constant, .sub.r tan [%] sample La KN temper- atmo- size 100 1 10 100 1 100 1 10 100 1 no. [mol %] [mol %] ature sphere [m] Hz kHz kHz kHz MHz Hz kHz kHz kHz MHz 4 5 5 1200 air 0.3 144 141 140 137 141 1.8 1.8 1.0 2.0 1.5 5 5 10 1200 air 0.3 199 195 193 191 193 1.1 2.1 4.4 2.3 0.2

(92) FIG. 10A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)BT-xKNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 10B is a graph illustrating changes in dielectric loss values.

(93) The sintering under the reducing atmosphere was performed under conditions of 1,200 C., 5H.sub.2-95N.sub.2, and 2 hours, and the subsequent heat treatment under the oxidizing atmosphere was performed under conditions of 1,050 or 1,100 C., N.sub.2, and 30 minutes, in 90BT-10KNN and 80BT-20KNN.

(94) Through the experiment, it was confirmed that in a particle size of 0.2 m to 1 m in a high frequency region of 1 MHz, a relative dielectric constant of 1,400 to 3,000 was exhibited, and a dielectric loss value of 10 to 20% was exhibited.

(95) FIG. 11A is a graph illustrating changes in relative dielectric constant values according to the addition of TEOS in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 11B is a graph illustrating changes in dielectric loss values.

(96) In 90BT-10KNN, the sintering under the reducing atmosphere and the subsequent heat treatment under the oxidizing atmosphere were performed under conditions of 1,200 C., 5H.sub.2-95N.sub.2, and 2 hours and under conditions of 1,100 C., N.sub.2, and 30 minutes, respectively, and the content of tetraethyl orthosilicate (TEOS) was measured at 0, 0.5, and 2 wt %. In comparison with FIG. 10A and FIG. 10B, in the case where a predetermined amount of TEOS was added, a relative dielectric constant of 1,900 to 3,200 and a dielectric loss of 10 to 18% were exhibited in a frequency region of 1 MHz.

(97) FIG. 12A is a graph illustrating changes in relative dielectric constant values when (100-x)BT-xKNN is subjected to pre-heat treatment (prefiring) as a pre-step of sintering in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 12B is a graph illustrating changes in dielectric loss values.

(98) When a pre-heat treatment (prefiring) process prior to sintering was performed under the same conditions as the conditions described in FIG. 11, the relative dielectric constant and the dielectric loss were measured. The pre-heat treatment (prefiring) was performed under conditions of 900 C., 5H.sub.2-95N.sub.2, and 5 hours.

(99) As an example, when the blue color graph (a relative dielectric constant when 2 wt % of TEOS was added) in FIG. 11A is compared with the black color graph (a relative dielectric constant when 2 wt % of TEOS was added) in FIG. 11A, it can be seen that when a pre-heat treatment (prefiring) prior to the sintering was performed, the change width of the dielectric constant is less than before, that is, the dielectric constant is relatively constantly maintained, regardless of the frequency region.

(100) FIG. 13A is a graph illustrating changes in relative dielectric constant values of 90BT-10KNN according to the sintering temperature performed under a reducing atmosphere when a subsequent heat treatment process is performed under a N.sub.2 oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 13B is a graph illustrating changes in dielectric loss values.

(101) The sintering was performed at a temperature of 1,200 C., 1,250 C., and 1,280 C. under a reducing atmosphere.

(102) In the following Table 3, data in FIGS. 10 to 13 are summarized.

(103) TABLE-US-00003 TABLE 3 composition and annealing condition ferroelectric additive 2nd firing dielectric characteristics material material condition grain .sub.r tan [%] sample KNN TEOS temper- atmo- size 1 1 1 1 no. [mol %] [wt %] ature sphere [m] kHz MHz kHz MHz 6 10 0 1100 N.sub.2 0.2 16,710 1,440 63.9 15.5 7 10 0 1050 N.sub.2 0.2 19,620 1,440 63.6 15.3 8 20 0 1100 N.sub.2 0.3 17,980 1,870 50.8 14.1 9 20 0 1050 N.sub.2 0.3 17,420 1,900 71.9 11.8 10 10 0.5 1100 N.sub.2 0.2 10,980 1,970 61.5 11.9 11 10 2 1100 N.sub.2 0.2 12,280 2,800 44.2 13.3 12 10 5 1100 N.sub.2 0.2 17,900 3,130 17.5 18.1 13 10 8 1100 N.sub.2 0.2 16,330 2,640 28.0 16.2

(104) FIG. 14A is a graph illustrating changes in relative dielectric constant values according to the frequency measured in (100-x)BT-xKNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 14B is a graph illustrating changes in dielectric loss values.

(105) The sintering under the reducing atmosphere was performed under conditions of 1,200 C., 5H.sub.2-95N.sub.2, and 2 hours, and the subsequent heat treatment under the oxidizing atmosphere was performed under conditions of 1,050 or 1,100 C., normal pressure (air), and 30 minutes, in 90BT-10KNN and 80BT-20KNN.

(106) Referring to FIG. 14, it can be confirmed that the relative dielectric constant and dielectric loss values are constantly maintained without a significant change, regardless of the frequency region. It was confirmed that numerically, in a particle size of 0.2 m to 1 m, the relative dielectric constant was maintained within a change width of about 0 to about 20, and the dielectric loss was maintained within a change width of about 0% to about 2%.

(107) FIG. 15A is a graph illustrating changes in relative dielectric constant values according to the addition of TEOS in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 15B is a graph illustrating changes in dielectric loss values.

(108) In 90BT-10KNN, the sintering under the reducing atmosphere and the heat treatment under the oxidizing atmosphere were performed under conditions of 1,200 C., 5H.sub.2-95N.sub.2, and 2 hours and under conditions of 1,100 C., normal pressure (air), and 30 minutes, respectively, and the content of tetraethyl orthosilicate (TEOS) was measured at 0, 0.5, and 2 wt %. In comparison with FIG. 14A and FIG. 14B, in the case where a predetermined amount of TEOS is added, it can be confirmed that in a frequency region of 1 MHz, a less change width is maintained than in a frequency region than in a range where the relative dielectric constant and the dielectric loss are high.

(109) FIG. 16A is a graph illustrating changes in relative dielectric constant values when (100-x)BT-xKNN is subjected to pre-heat treatment (prefiring) as a pre-step of sintering in 90BT-10KNN in which an oxidizing atmosphere of a subsequent heat treatment process consists of a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 16B is a graph illustrating changes in dielectric loss values.

(110) When a pre-heat treatment (prefiring) process prior to sintering was performed under the same conditions as the conditions described in FIG. 15, the relative dielectric constant and the dielectric loss were measured. The pre-heat treatment (prefiring) was performed under conditions of 900 C., 5H.sub.2-95N.sub.2, and 5 hours.

(111) When compared with FIG. 15, it can be confirmed that when the pre-heat treatment (prefiring) prior to sintering is performed, a less change width is maintained than in a range where the relative dielectric constant and the dielectric loss are high.

(112) FIG. 17A is a graph illustrating changes in relative dielectric constant values of 90BT-10KNN according to the sintering temperature under a reducing atmosphere when a subsequent heat treatment process is performed under a normal pressure (air) oxidizing atmosphere in (100-x)BT-xKNN, and FIG. 17B is a graph illustrating changes in dielectric loss values.

(113) The sintering was performed at a temperature of 1,200 C., 1,250 C., and 1,280 C. under a reducing atmosphere.

(114) In the following Table 4, data in FIGS. 14 to 17 are summarized.

(115) TABLE-US-00004 TABLE 4 composition and annealing condition dielectric characteristics ferroelectric additive 2nd firing dielectric Dielectric loss, material material condition grain constant, .sub.r tan [%] sample KNN TEOS temper- atmo- size 100 1 10 100 1 100 1 10 100 1 no. [mol %] [wt %] ature sphere [m] Hz kHz kHz kHz MHz Hz kHz kHz kHz MHz 14 10 0 1100 air 0.2 297 297 296 294 300 1.6 1.5 0.9 1.8 0.4 15 10 0 1050 air 0.2 329 315 314 311 317 1.8 1.6 1.1 1.8 0.8 16 20 0 1100 air 0.3 387 375 378 378 381 1.1 1.6 1.2 0.3 0.7 17 20 0 1050 air 0.3 370 363 365 366 368 1.2 1.4 1.2 0.4 1.1 18 10 0.5 1100 air 0.2 438 434 433 423 433 0.5 0.5 0.6 1.9 0.7 19 10 2 1100 air 0.2 511 509 506 503 504 0.5 0.6 0.7 0.5 1.0 20 10 5 1100 air 0.2 595 586 583 580 582 1.4 0.9 0.7 0.4 0.4 21 10 8 1100 air 0.2 444 441 439 437 439 1.1 0.5 0.6 0.3 0.3

(116) Representative exemplary embodiments of the present invention have been described in detail, but it is to be understood by a person with ordinary skill in the art to which the present invention pertains that various modifications are possible with respect to the above-described example within the limitation without departing from the scope of the present invention. Therefore, the right scope of the present invention should not be defined by being limited to the described Examples, and should be defined by not only the claims to be described below, but also those equivalent to the claims.