Dielectric ceramic material

Abstract

A dielectric ceramic material includes the composite ceramic powder of BaTiO.sub.3 and Ba.sub.2LiTa.sub.5O.sub.15, or BaTiO.sub.3 and Ba.sub.2LiNb.sub.5O.sub.15 that are based on the oxides of BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5, or BaO, TiO.sub.2, Li.sub.2O and Nb.sub.2O5 as initial powder materials prepared subject to a respective predetermined percentage. This dielectric ceramic material simply uses simple binary oxides as initial powder materials that are easy to obtain and inexpensive, and that eliminate the complicated manufacturing process of synthesizing BaTiO.sub.3, Ba.sub.2LiTa.sub.5O.sub.15 or Ba.sub.2LiNb.sub.5O.sub.15, making the whole process more simple and the manufacturing cost more cheaper and preventing the formation of other compounds.

Claims

1. A dielectric ceramic material, comprising BaTiO.sub.3 and Ba.sub.2LiTa.sub.5O.sub.15, wherein the mole percentage matches a composition formula of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15), x is 0.030.05.

2. The dielectric ceramic material as claimed in claim 1, wherein said BaTiO.sub.3 and said Ba.sub.2LiTa.sub.5O.sub.15 are respectively prepared by the initial oxide powders of BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5 at a respective predetermined percentage.

3. A dielectric ceramic material, comprising BaTiO.sub.3 and Ba.sub.2LiTa.sub.5O.sub.15, wherein the mole percentage matches a composition formula of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15), x is 0.100.20.

4. The dielectric ceramic material as claimed in claim 3, wherein said BaTiO.sub.3 and said Ba.sub.2LiTa.sub.5O.sub.15 are respectively prepared by the initial oxide powders of BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5 at a respective predetermined percentage.

5. A dielectric ceramic material, comprising BaTiO.sub.3 and Ba.sub.2LiTa.sub.5O.sub.15, wherein the mole percentage matches a composition formula of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15), x is 0.260.50.

6. The dielectric ceramic material as claimed in claim 5, wherein said BaTiO.sub.3 and said Ba.sub.2LiTa.sub.5O.sub.15 are respectively prepared by the initial oxide powders of BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5 at a respective predetermined percentage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a tablet-shaped capacitor preparation flow chart in accordance with the present invention.

(2) FIG. 2 illustrates an alternate form of the tablet-shaped capacitor preparation flow chart in accordance with the present invention.

(3) FIG. 3 is a multilayer ceramic capacitor (MLCC) preparation flow chart in accordance with the present invention.

(4) FIG. 4 illustrates an alternate form of the multilayer ceramic capacitor (MLCC) preparation flow chart in accordance with the present invention.

(5) FIG. 5 is a schematic sectional view of a multilayer ceramic capacitor (MLCC) in accordance with the present invention.

(6) FIG. 6 is a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) (x=0.030.15) in accordance with the present invention.

(7) FIG. 7 is a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) (x=0.200.50) in accordance with the present invention.

(8) FIG. 8 is a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) (x=0.010.25) in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(9) Referring to FIGS. 1-5, a tablet-shaped capacitor preparation flow chart, an alternate form of the tablet-shaped capacitor preparation flow chart, a multilayer ceramic capacitor (MLCC) preparation flow chart and an alternate form of the multilayer ceramic capacitor (MLCC) preparation flow chart in accordance with the present invention as illustrated. As illustrated, during the preparation of the composite dielectric ceramic material, BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5, or BaO, TiO.sub.2, Li.sub.2O and Nb.sub.2O.sub.5 are well mixed to form an initial powder material, and then this initial powder material is used to prepare the composite dielectric ceramic material (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x (Ba.sub.2LiNb.sub.5O.sub.15) subject to the formulas of Table 2 and Table 3, wherein Table 2 is the oxide ingredient recipe table for the preparation of 100 mole (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15); Table 3 is the oxide ingredient recipe table for the preparation of 100 mole (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15).

(10) Referring to FIGS. 1 and 2 again, 20 g composite dielectric ceramic powder prepared subject to Table 2 and Table 3 is put in a cylindrical polyethylene bottle of diameter 50 mm and volume 200 ml, and then 200 g Zirconia balls of diameter 3 mm are put in the cylindrical polyethylene bottle for use as grinding elements, and then ethanol is added to the cylindrical polyethylene bottle for use as a mixed solvent, and then the cylindrical polyethylene is rotated at 360 rpm for 6 hours to well mix the dielectric ceramic powder. The well mixed dielectric ceramic power is then dried at 80 C. Thereafter, prepare a ceramic embryogenic tablet by: adding 5 wt % polyvinyl alcohol (PVA) aqueous binder (water solution prepared by 15 wt % PVA and 85 wt % pure water) to the prepared dielectric ceramic powder and then well mixing the applied materials to enhance powder formability, and then using a 80 mesh stainless steel screen prepared subject to the specifications of American Society for Testing and Materials (ASTM) to screen the powder material, and then taking 0.4 g of the screened powder to cast a round embryogenic tablet of diameter 10 mm using a uniaxial molding method, and then heating the round embryogenic tablet under the atmosphere environment at 550 C. for 4 hours (at the heating rate of 5 C./min) to burn out polyvinyl alcohol (PVA) aqueous binder, and then sintering the round embryogenic tablet under a reducing atmosphere composed of 98% N.sub.2-2% H.sub.2 and 35 C. saturated water vapor at 1100 C.1400 C. (at the heating rate of 5 C./min) for 2 hours, and then applying an reoxidation heat treatment to the sintered ceramic body under 60 ppm-150 ppm or atmospheric environment at 900 C.1050 C. (at the heating rate of 5 C./min), and then using a screen-printing technique to print Ag, Cu or Ni on the sintered ceramic body so as to form an electrode on each of two opposite parallel sides of the sintered ceramic body. Thus, tablet-shaped capacitor examples according to Table 2 and Table 3 can then be prepared.

(11) TABLE-US-00002 TABLE 2 (1 x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) Formula Table (1 x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) Unit: mole Examples X value BaO TiO.sub.2 Li.sub.2O Ta.sub.2O.sub.5 Example 1 x = 0.030 97.00 97.00 1.50 7.50 Example 2 x = 0.050 95.00 95.00 2.50 12.50 Example 3 x = 0.100 90.00 90.00 5.00 25.00 Example 4 x = 0.125 87.50 87.50 0.625 31.25 Example 5 x = 0.150 85.00 85.00 7.50 37.50 Example 6 x = 0.200 80.00 80.00 10.00 50.00 Example 7 x = 0.260 74.00 74.00 13.00 65.00 Example 8 x = 0.300 70.00 70.00 15.00 75.00 Example 9 x = 0.400 60.00 60.00 20.00 100.00 Example x = 0.500 50.00 50.00 25.00 125.00 10

(12) TABLE-US-00003 TABLE 3 (1 x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) Formula Table (1 x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) Unit: mole Examples X value BaO TiO.sub.2 Li.sub.2O Nb.sub.2O.sub.5 Example 11 x = 0.010 99.00 99.00 0.50 2.50 Example 12 x = 0.100 90.00 90.00 5.00 25.00 Example 13 x = 0.200 80.00 80.00 10.00 50.00 Example 14 x = 0.250 75.00 75.00 12.50 67.50

(13) Further, when using the composite dielectric ceramic material to make multilayer ceramic capacitor (MLCC) examples, use initial powder materials of at least two group materials including BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5, or, BaO, TiO.sub.2, Li.sub.2O and Nb.sub.2O.sub.5 to prepare composite dielectric ceramic powders (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) according to the formula tables of Table 2 and Table 3 and the preparation flow charts of FIG. 3 and FIG. 4. Thereafter, add ethanol, plasticizing agents, bonding agents and dispersing agents to each prepared composite dielectric ceramic powder to obtain a respective ceramic slurry, and then use a tap casting method to mold each ceramic slurry into thin ceramic green sheets of thickness 30 m, and then use a screen-printing technique to print commercial Ag, Pd or Ni metal paste on the thin ceramic green sheets embryonic strips subject to a predetermined internal electrode pattern.

(14) Thereafter, stack up printed thin ceramic green sheets, and then use hydrostatic pressure to compress the stacked, printed thin ceramic green sheets, and then cut the stacked, printed thin ceramic green sheets into designed multilayer ceramic green chip, and then heat the multilayer ceramic green chip under the pure N.sub.2 atmosphere at 330 C. (at the heating rate of 2 C./min) for 12 hours to burn out organic matters, and then sinter the multilayer ceramic green chip under a reducing atmosphere composed of 98% N.sub.2-2% H.sub.2 and 35 C. saturated water vapor at 1100 C.1400 C. (at the heating rate of 3 C./min) for 2 hours and then reduce the heating the temperature to 900 C.1050 C. (at the cooling rate of 4 C./min), and then apply an reoxidation heat treatment to the sintered bulk under 60 ppm150 ppm or air atmosphere environment, and then reduce the temperature to room temperature to obtain multilayer ceramic sintered bulk. Thereafter, dip Ag or Cu external electrode paste on exposed ends of the internal electrodes, and then raise the temperature to 800 C.900 C. (at the heating rate of 15 C./min) under the pure N.sub.2 atmosphere, and then cool down the stove to room temperature, and the desired multilayer ceramic capacitor (MLCC) examples are prepared.

(15) Referring to FIGS. 6-8, a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) (x=0.030.15), a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) (x=0.200.50) and a dielectric characteristic measurement diagram of the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) (x=0.010.25) in accordance with the present invention are illustrated. As illustrated, when measuring the prepared composite dielectric ceramic capacitors of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15), use a LCR meter to measure temperature coefficient of capacitance (TCC) of every composite dielectric ceramic capacitor example, and then apply 1V at 1 kHz to measure the variation of capacitance value relative to temperature at 55 C.200 C. and the dielectric-loss factor (DF) at room temperature.

(16) Referring to the following Table 4 and FIGS. 6 and 7, measurement results of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) examples 110 are illustrated. From these measurement results, it is apparent that when x=0.030.05, the prepared dielectric ceramic capacitors have optimal dielectric characteristic stability and can satisfy EIA X8S specifications. It is apparent that increasing the proportion of Ba.sub.2LiTa.sub.5O.sub.15 can get composite dielectric ceramic capacitors that have better temperature stability; when increasing x value from 0.03 to 0.05 (examples 12), the characteristics of the prepared capacitors are changed from satisfying X8S specifications to X8R specifications; when increasing the proportion of Ba.sub.2LiTa.sub.5O.sub.15 to x=0.100.20 (examples 36), it can get capacitors that satisfy EIA X9R specifications; when x=0.260.50 (examples 710), the Temperature Coefficient of Capacitance (TCC) at 55 C.25 C. TCC is gradually shifted toward the positive value, or toward the negative value when at 55 C.200 C., enabling the characteristics of the prepared capacitors to be changed from satisfying X9R specifications to X9S and X9T specifications. From these results, we can know that a composite dielectric ceramic capacitor based on the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) according to the present invention has excellent dielectric characteristic stability with dielectric-loss factor (DF) within 1.5% when x value=0.030.50 (examples 110), it can effectively stabilize the dielectric characteristics; when x value is increased from 0.10 to 0.20, the most optimal dielectric characteristic stability can be obtained to satisfy EIA X9R specifications.

(17) TABLE-US-00004 TABLE 4 Dielectric characteristics of (1 x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) EIA 25 C. 55 C. 125 C. 150 C. 200 C. Example BaTiO.sub.3 Ba.sub.2LiTa.sub.5O.sub.15 Spec K DF TCC TCC TCC TCC 1 0.97 0.03 X8S 1076 0.49% 4.2% 13.2% 20.3% 47.5% 2 0.95 0.05 X8R 571 0.37% 4.6% 10.6% 13.5% 35.5% 3 0.90 0.10 X9R 150 0.18% 7.1% 6.8% 8.9% 14.9% 4 0.875 0.125 X9R 116 0.74% 5.4% 6.9% 9.0% 14.4% 5 0.85 0.15 X9R 312 0.48% 5.8% 3.1% 3.1% 7.3% 6 0.80 0.20 X9R 252 0.28% 9.2% 8.6% 5.6% 8.6% 7 0.74 0.26 X9S 206 0.16% 12.3% 11.5% 12.5% 16.3% 8 0.70 0.30 X9T 192 0.13% 16.3% 13.3% 16.1% 21.6% 9 0.60 0.40 X9T 219 0.56% 17.4% 13.6% 16.5% 21.9% 10 0.50 0.50 X9T 212 1.02% 17.7% 16.7% 18.6% 25.5%

(18) Referring to the following Table 5 with reference to FIG. 8, from the measurement results made on examples 1114 (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15), it can be known that increasing the percentage of Ba.sub.2LiNb.sub.5O.sub.15 can get a capacitor with ultra stable dielectric characteristics. When x=0.01, the prepared dielectric ceramic capacitor has optimal dielectric characteristic stability and can satisfy EIA X8S specifications. It is apparent that increasing the proportion of Ba.sub.2LiNb.sub.5O.sub.15 to over 0.10 can get a capacitor of significantly stable dielectric characteristic curve that satisfies EIA X9R specifications. From this result we can know that a composite dielectric ceramic capacitor based on the dielectric ceramic material of (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) according to the present invention has excellent dielectric characteristic stability with dielectric-loss factor (DF) within 1.5%; when x value=0.01, it can effectively stabilize the dielectric characteristics; when x value is above 0.10, the most optimal dielectric characteristic stability can be obtained to satisfy EIA X9R specifications.

(19) TABLE-US-00005 TABLE 5 Dielectric characteristics of (1 x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) EIA 25 C. 55 C. 125 C. 150 C. 200 C. Example BaTiO.sub.3 Ba.sub.2LiNb.sub.5O.sub.15 Spec K DF TCC TCC TCC TCC 11 0.99 0.01 X8S 1383 0.50% 1.3% 13.4% 21.9% 57.8% 12 0.90 0.10 X9R 148 0.24% 5.9% 7.2% 9.0% 12.8% 13 0.80 0.20 X9R 222 0.27% 5.8% 4.6% 5.4% 5.0% 14 0.75 0.25 X9R 489 1.30% 10.0% 8.7% 9.1% 7.7%

(20) The above-described (1x)(BaTiO.sub.3)x(Ba2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) capacitors and their initial oxide powder materials are not intended for use to limit the scope and spirit of the present invention. The most optimal form of the present invention is to use initial powder materials of at least two group materials including BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5, or, BaO, TiO.sub.2, Li.sub.2O and Nb.sub.2O.sub.5 to prepare composite dielectric ceramic powders (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15).

(21) In accordance with the popular ceramic material common sense can infer that sintering BaO, TiO.sub.2, Li.sub.2O, Ta.sub.2O.sub.5 and Nb.sub.2O.sub.5 can produce various compounds, such as the oxides of BaTiO.sub.3, BaTa.sub.2O.sub.6, BaNb.sub.2O.sub.6, Ba(Ti.sub.0.5Nb.sub.0.5)O.sub.3, Li.sub.2TiO.sub.3, Li.sub.4TiO.sub.4, LiTaO.sub.3 and LiNbO.sub.3. These oxides can be used as initial powder materials for making (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x(Ba.sub.2LiNb.sub.5O.sub.15) capacitors subject to a predetermined percentage. In actual application, carbonates of BaCO.sub.3, BaCl.sub.2, Li.sub.2CO.sub.3 and LiOH, chlorides and hydroxides can be converted into oxides under a high temperature. Therefore, these oxides can be prepared in accordance with the corresponding proportion of the respective metal element as initial powder materials for the (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO3)x(Ba.sub.2LiNB.sub.5O.sub.15) capacitors

(22) Therefore, the invention provides dielectric ceramic materials of (1x)(BaTiO.sub.3)x(Ba.sub.2LiTa.sub.5O.sub.15) and (1x)(BaTiO.sub.3)x (Ba.sub.2LiTa.sub.5O.sub.15) that comprise BaO, TiO.sub.2, Li.sub.2O and Ta.sub.2O.sub.5, or Bao, TiO.sub.2, Li.sub.2O and Nb.sub.2O.sub.5 as the initial oxide powders, and is prepared in accordance with the corresponding proportion of the respective metal element. These dielectric ceramic materials simply use simple binary oxides as initial powder materials that are easy to obtain and inexpensive, and that eliminate the complicated manufacturing process of using other oxides of BaTiO.sub.3 and LiTaO.sub.3 or BaTiO.sub.3, Li.sub.2CO.sub.3 and Ta.sub.2O.sub.5 as the initial powder materials to synthesize BaTiO.sub.3, Ba.sub.2LiTa5O.sub.15 and Ba.sub.2LiNb.sub.5O.sub.15, making the whole process more simple and the manufacturing cost more cheaper and preventing the formation of other compounds (Such as Li.sub.3TaO.sub.4). These dielectric ceramic materials are very practical for industrial application and have great commercial value, making the products more competitive.

(23) Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.