Ni—Zn—Cu-based ferrite particles, green sheet comprising the Ni—Zn—Cu-based ferrite particles and Ni—Zn—Cu-based ferrite sintered ceramics

Abstract

An object of the present invention is to provide a ferrite material that is excellent in temperature characteristic and DC superimposition characteristic. The present invention relates to NiZnCu-based ferrite particles comprising 70 to 95% by weight of an NiZnCu ferrite having a specific composition, 1 to 20% by weight of nickel oxide, 0 to 20% by weight of zinc oxide and 1 to 10% by weight of copper oxide, and a ferrite sintered ceramics obtained by sintering the ferrite particles.

Claims

1. NiZnCu-based ferrite particles comprising: (a) 70 to 95% by weight of an NiZnCu ferrite, wherein the NiZnCu ferrite has a composition comprising 35 to 45 mol % of Fe.sub.2O.sub.3, 10 to 20 mol % of NiO, 30 to 40 mol % of ZnO, and 6 to 15 mol % of CuO in terms of the respective oxides; (b) 1 to 20% by weight of nickel oxide; and (c) 1 to 10% by weight of copper oxide.

2. NiZnCu-based ferrite particles comprising: (a) 70 to 95% by weight of an NiZnCu ferrite, wherein the NiZnCu ferrite has a composition comprising 35 to 45 mol % of Fe.sub.2O.sub.3, 10 to 20 mol % of NiO, 30 to 40 mol % of ZnO and 6 to 15 mol % of CuO in terms of the respective oxides; (b) 1 to 20% by weight of nickel oxide; (c) not more than 20% by weight of zinc oxide; and (d) 1 to 10% by weight of copper oxide.

3. A green sheet comprising the NiZnCu-based ferrite particles as defined in claim 1 and a binder material which are formed into a sheet shape.

4. An NiZnCu-based ferrite sintered ceramics comprising: (a) 70 to 95% by weight of an NiZnCu ferrite, wherein the NiZnCu ferrite has a composition comprising 35 to 45 mol % of Fe.sub.2O.sub.3, 10 to 20 mol % of NiO, 30 to 40 mol % of ZnO and 6 to 15 mol % of CuO in terms of the respective oxides; (b) 1 to 20% by weight of nickel oxide; and (c) 1 to 10% by weight of copper oxide.

5. An NiZnCu-based ferrite sintered ceramics comprising: (a) 70 to 95% by weight of an NiZnCu ferrite, wherein the NiZnCu ferrite has a composition comprising 35 to 45 mol % of Fe.sub.2O.sub.3, 10 to 20 mol % of NiO, 30 to 40 mol % of ZnO and 6 to 15 mol % of CuO in terms of the respective oxides; (b) 1 to 20% by weight of nickel oxide; (c) not more than 20% by weight of zinc oxide; and (d) 1 to 10% by weight of copper oxide.

6. The NiZnCu-based ferrite sintered ceramics according to claim 4, wherein a magnetic permeability .sub.0 of the NiZnCu-based ferrite sintered ceramics as measured under the condition that no DC superimposition magnetic field is applied thereto is in the range of 20 to 170; a core loss P.sub.0 of the NiZnCu-based ferrite sintered ceramics as measured under the condition that no DC superimposition magnetic field is applied thereto is not more than 500 kW/m.sup.3; a ratio of a magnetic permeability .sub.1000 of the NiZnCu-based ferrite sintered ceramics as measured under the condition that a DC superimposition magnetic field of 1000 A/m is applied thereto to the magnetic permeability .sub.0 (.sub.1000/.sub.0) is not less than 0.4; a ratio of a core loss P.sub.1000 of the NiZnCu-based ferrite sintered ceramics as measured under the condition that a DC superimposition magnetic field of 1000 A/m is applied thereto to the core loss P.sub.0 (P.sub.1000/P.sub.0) is in the range of 0.7 to 2.0; and a rate of change in the magnetic permeability .sub.0 relative to a temperature as measured at 100 C. is not more than 10%.

Description

EXAMPLES

(1) Typical embodiments of the present invention are as follows.

(2) The crystal phases forming the NiZnCu-based ferrite particles and the NiZnCu-based ferrite sintered ceramics and the contents of the crystal phases therein were measured using an X-ray diffraction apparatus D8 ADVANCE (manufactured by BRUKER AXS GmbH), and evaluated by Rietveld analysis using a software TOPAS attached to the apparatus.

(3) The compositions of NiZnCu ferrite in the NiZnCu-based ferrite particles and the NiZnCu-based ferrite sintered ceramics were calculated from contents of the respective elements as measured using a fluorescent X-ray analyzer 3530 (manufactured by Rigaku Denki Kogyo Co., Ltd.), and contents of the respective crystal phases determined by Rietveld analysis.

(4) The BET specific surface area of the NiZnCu-based ferrite particles was measured using a 4-specimen automatic specific surface area measurement and 8-specimen simultaneous deaeration apparatus 4-SORB U2 (manufactured by Yuasa Ionix Co., Ltd.).

(5) The sintered density of the NiZnCu-based ferrite sintered ceramics was calculated from a volume of a sample which were measured from an outer diameter thereof and a weight.

(6) The magnetic permeability .sub.0 of the NiZnCu-based ferrite sintered ceramics was determined as follows. That is, a magnetic permeability of a ring-shaped sintered ceramics around which a coil was wound was measured at 25 C. at a frequency of 1 MHz and a magnetic flux density of 15 mT using a B-H analyzer SY-8232 (manufactured by IWATSU TEST INSTRUMENTS CORP.), under the condition that no DC superimposition magnetic field was applied thereto, and the value of the thus measured amplitude ratio magnetic permeability was determined as .sub.0.

(7) The magnetic permeability .sub.1000 of the NiZnCu-based ferrite sintered ceramics was determined as follows. That is, a magnetic permeability of a ring-shaped sintered ceramics around which a coil was wound was measured at 25 C. at a frequency of 1 MHz and a magnetic flux density of 15 mT using a B-H analyzer SY-8232 (manufactured by IWATSU TEST INSTRUMENTS CORP.) under the condition that a DC superimposition magnetic field of 1000 A/m was applied thereto, and the value of the thus measured amplitude ratio magnetic permeability was determined as .sub.1000. The ratio .sub.1000/.sub.0 was calculated from .sub.0 and .sub.1000 thus measured.

(8) The core loss P.sub.0 of the NiZnCu-based ferrite sintered ceramics was determined as follows. That is, a core loss of a ring-shaped sintered ceramics around which a coil was wound was measured at 25 C. at a frequency of 1 MHz and a magnetic flux density of 15 mT using a B-H analyzer SY-8232 (manufactured by IWATSU TEST INSTRUMENTS CORP.) under the condition that no DC superimposition magnetic field was applied thereto, and the thus measured P.sub.cv value was determined as P.sub.0.

(9) The core loss P.sub.1000 of the NiZnCu-based ferrite sintered ceramics was determined as follows. That is, a core loss of a ring-shaped sintered ceramics around which a coil was wound was measured at 25 C. at a frequency of 1 MHz and a magnetic flux density of 15 mT using a B-H analyzer SY-8232 (manufactured by IWATSU TEST INSTRUMENTS CORP.) under the condition that a DC superimposition magnetic field of 1000 A/m was applied thereto, and the thus measured P.sub.cv value was determined as P.sub.1000. The ratio P.sub.1000/P.sub.0 was calculated from P.sub.0 and P.sub.1000 thus measured.

(10) The temperature characteristic of a magnetic permeability of the NiZnCu-based ferrite sintered ceramics was determined as follows. That is, an amplitude ratio magnetic permeability of a ring-shaped sintered ceramics around which a coil was wound was measured at 25 C. and 100 C. at a frequency of 1 MHz and a magnetic flux density of 15 mT using a B-H analyzer SY-8232 (manufactured by IWATSU TEST INSTRUMENTS CORP.) under the condition that no DC superimposition magnetic field was applied thereto, and the temperature characteristic of a magnetic permeability was calculated from the thus measured amplitude ratio magnetic permeability.

Example 1-1

Production of NiZnCu-Based Ferrite Particles

(11) The respective oxide raw materials were weighed such that NiZnCu-based ferrite obtained therefrom had a predetermined composition, and wet-mixed with each other for 20 hr using a ball mill. The resulting mixed slurry was filtered to separate a solid component therefrom, and the thus separated solid component was dried to obtain raw mixed particles. The thus obtained raw mixed particles were calcined at 830 C. for 4 hr, and the resulting pre-calcined product was pulverized using a ball mill, thereby obtaining NiZnCu-based ferrite particles according to the present invention.

(12) The content of NiZnCu ferrite in the thus obtained NiZnCu-based ferrite particles was 84.7% by weight, and the NiZnCu ferrite had a composition comprising 40.9 mol % of Fe.sub.2O.sub.3, 14.7 mol % of NiO, 35.7 mol % of ZnO and 8.7 mol % of CuO. Also, the content of nickel oxide in the ferrite particles was 5.1% by weight, the content of zinc oxide therein was 6.4% by weight, and the content of copper oxide therein was 3.8% by weight. Further, the BET specific surface area of the NiZnCu-based ferrite particles was 4.9 m.sup.2/g.

Example 2-1

Production of Green Sheet

(13) Eight parts by weight of polyvinyl butyral as a binder material, 3 parts by weight of benzyl-n-butyl phthalate as a plasticizer and 50 parts by weight of 3-methyl-3-methoxy-1-butanol as a solvent were added to 100 parts by weight of the NiZnCu-based ferrite particles obtained in Example 1-1, and the resulting mixture was fully mixed to obtain a slurry. The thus obtained slurry was applied onto a PET film using a doctor blade-type coater to form a coating film thereon. The coating film was then dried to obtain a green sheet having a thickness of 75 m. The thus obtained ten green sheets each cut into a size of 100 mm in length100 mm in width, were laminated and then pressed together under a pressure of 0.3510.sup.4 t/m.sup.2, thereby obtaining a green sheet laminate having a thickness of 0.74 mm.

(14) <Production of NiZnCu-Based Ferrite Sintered Ceramics>

(15) The above obtained green sheet laminate was sintered at 900 C. for 2 hr, thereby obtaining a NiZnCu-based ferrite sintered ceramics having a thickness of 0.62 m. The content of NiZnCu ferrite in the thus obtained NiZnCu-based ferrite sintered ceramics was 84.1% by weight, and the NiZnCu ferrite had a composition comprising 40.9 mol % of Fe.sub.2O.sub.3, 15.0 mol % of NiO, 35.4 mol % of ZnO and 8.7 mol % of CuO. Also, the content of nickel oxide in the sintered ceramics was 3.7% by weight, the content of zinc oxide therein was 8.7% by weight, and the content of copper oxide therein was 3.5% by weight. Also, the sintered density of the NiZnCu-based ferrite sintered ceramics was 5.1 g/cm.sup.3. Further, the NiZnCu-based ferrite sintered ceramics was cut into a ring-shaped sintered ceramics having an outer diameter of 14 mm, an inner diameter of 8 mm and a thickness of 0.62 mm using an ultrasonic machine to evaluate magnetic properties thereof. As a result, it was confirmed that the sintered ceramics had .sub.0 of 98, a ratio .sub.1000/.sub.0 of 0.70, a core loss P.sub.0 of 140 kW/m.sup.3 and a ratio P.sub.1000/P.sub.0 of 1.00. Also, it was confirmed that the rate of change in magnetic permeability of the NiZnCu-based ferrite sintered ceramics was 2.1%.

Examples 1-2 to 1-6 and Comparative Examples 1-1 to 1-5

(16) The same procedure as in Example 1-1 was conducted except that the compositional ratios were changed variously, thereby obtaining NiZnCu-based ferrite particles. Various properties of the thus obtained NiZnCu-based ferrite particles are shown in Table 1.

Examples 2-2 to 2-5

(17) Respective NiZnCu-based ferrite sintered bodies were produced by the same method as defined in Example 2-1. The production conditions used in these Examples are shown in Table 2, and various properties of the thus obtained NiZnCu-based ferrite sintered bodies are shown in Table 3.

Example 2-6

(18) One hundred parts by weight of the NiZnCu-based ferrite particles produced in the same manner as in Example 1-1 were mixed with 10 parts by weight of a 6% polyvinyl alcohol aqueous solution to obtain mixed particles. Then, 7.0 g of the thus obtained mixed particles were press-molded in a metal mold under a pressure of 1.010.sup.4 t/m.sup.2 to obtain a disk-shaped molded product having an outer diameter of 30 mm and a thickness of 2.9 mm. The thus obtained molded product was sintered at 900 C. for 2 hr, thereby obtaining a NiZnCu-based ferrite sintered ceramics.

(19) The composition, crystal phase and sintered density of the thus obtained NiZnCu-based ferrite sintered ceramics were measured, and then the sintered ceramics was cut into a ring-shaped sintered ceramics having an outer diameter of 14 mm, an inner diameter of 8 mm and a thickness of 2 mm using an ultrasonic machine to evaluate magnetic properties thereof.

(20) The production conditions used in this Example are shown in Table 2, and various properties of the thus obtained NiZnCu-based ferrite sintered ceramics are shown in Table 3.

Comparative Examples 2-1 and 2-5

(21) Respective NiZnCu-based ferrite sintered bodies were produced in the same manner as defined in Example 2-1 or Example 2-6. The production conditions used in these Comparative Examples are shown in Table 2, and various properties of the thus obtained NiZnCu-based ferrite sintered bodies are shown in Table 3.

(22) TABLE-US-00001 TABLE 1 Properties of NiZnCu-based ferrite particles NiZnCu ferrite Content Fe.sub.2O.sub.3 NiO ZnO CuO No. [wt %] [mol %] [mol %] [mol %] [mol %] Example 1-1 84.7 40.9 14.7 35.7 8.7 Example 1-2 75.0 37.3 12.5 37.5 12.7 Example 1-3 92.7 42.7 17.6 32.3 7.4 Example 1-4 82.7 41.0 17.3 32.8 8.9 Example 1-5 75.5 37.8 12.6 36.8 12.8 Example 1-6 91.3 40.2 12.0 38.0 9.8 Comp. 64.5 31.3 20.1 40.1 8.5 Example 1-1 Comp. 98.4 45.6 9.5 29.5 15.4 Example 1-2 Comp. 57.5 35.0 15.8 39.1 10.2 Example 1-3 Comp. 84.2 41.9 18.6 34.0 5.5 Example 1-4 Comp. 100.0 49.0 25.5 16.5 9.0 Example 1-5 Properties of NiZnCu-based ferrite particles Nickel Zinc Copper oxide oxide oxide BET No. [wt %] [wt %] [wt %] [m.sup.2/g] Example 1-1 5.1 6.4 3.8 4.9 Example 1-2 6.3 14.4 4.3 7.6 Example 1-3 2.0 4.1 1.2 4.5 Example 1-4 14.6 0.0 2.7 5.5 Example 1-5 2.3 14.5 7.7 5.1 Example 1-6 2.1 5.1 1.5 3.3 Comp. 21.4 10.0 4.1 4.1 Example 1-1 Comp. 0.8 0.3 0.5 7.6 Example 1-2 Comp. 11.6 20.5 10.4 4.6 Example 1-3 Comp. 5.4 6.3 4.1 5.1 Example 1-4 Comp. 0.0 0.0 0.0 4.9 Example 1-5

(23) TABLE-US-00002 TABLE 2 Production conditions of NiZnCu-based ferrite Sintering temperature No. Molding method [ C.] Sintering time Example 2-1 Green sheet 900 2 method Example 2-2 Green sheet 870 2 method Example 2-3 Green sheet 880 5 method Example 2-4 Green sheet 900 2 method Example 2-5 Green sheet 1010 3 method Example 2-6 Powder press- 960 2 molding method Comp. Green sheet 890 4 Example 2-1 method Comp. Green sheet 900 2 Example 2-2 method Comp. Green sheet 930 2 Example 2-3 method Comp. Powder press- 900 3 Example 2-4 molding method Comp. Green sheet 890 4 Example 2-5 method

(24) TABLE-US-00003 TABLE 3 Properties of NiZnCu-based ferrite sintered ceramics NiZnCu ferrite Content Fe.sub.2O.sub.3 NiO ZnO CuO No. [wt %] [mol %] [mol %] [mol %] [mol %] Example 2-1 84.1 40.9 15.0 35.4 8.7 Example 2-2 75.1 37.3 12.2 37.8 12.7 Example 2-3 92.6 42.7 17.6 32.3 7.4 Example 2-4 82.4 41.1 17.2 32.9 8.8 Example 2-5 75.0 37.8 12.6 36.8 12.8 Example 2-6 90.7 40.2 12.0 38.0 9.8 Comp. 63.0 31.4 20.0 40.1 8.5 Example 2-1 Comp. 98.4 45.6 9.5 29.5 15.4 Example 2-2 Comp. 57.6 35.0 15.7 39.1 10.2 Example 2-3 Comp. 82.5 42.0 18.8 33.7 5.5 Example 2-4 Comp. 100.0 48.9 25.3 16.2 9.6 Example 2-5 Properties of NiZnCu-based ferrite sintered ceramics Nickel Zinc Copper Sintered oxide oxide oxide density No. [wt %] [wt %] [wt %] [g/cm.sub.3] Example 2-1 3.7 8.7 3.5 5.12 Example 2-2 8.0 12.1 4.8 4.94 Example 2-3 2.2 3.8 1.4 5.08 Example 2-4 14.9 0.0 2.7 5.09 Example 2-5 2.5 14.7 7.8 5.23 Example 2-6 2.3 5.4 1.6 5.15 Comp. 21.8 10.8 4.4 5.02 Example 2-1 Comp. 0.8 0.3 0.5 5.12 Example 2-2 Comp. 11.8 20.3 10.3 5.19 Example 2-3 Comp. 4.2 8.7 4.6 4.85 Example 2-4 Comp. 0.0 0.0 0.0 5.11 Example 2-5 Properties of NiZnCu-based ferrite sintered ceramics Temperature characteristic DC of magnetic superimposition permeability P.sub.0 characteristic No. .sub.0 [%] [kW/m.sup.3] .sub.1000/.sub.0 P.sub.1000/P.sub.0 Example 2-1 98 2.1 140 0.70 1.00 Example 2-2 124 4.9 199 0.61 1.52 Example 2-3 71 1.3 108 0.79 1.03 Example 2-4 30 0.3 210 0.95 0.83 Example 2-5 149 6.1 302 0.57 1.67 Example 2-6 158 7.4 343 0.42 1.84 Comp. 14 0.1 232 0.96 1.03 Example 2-1 Comp. 184 13.5 503 0.33 2.30 Example 2-2 Comp. 17 0.2 211 0.97 1.10 Example 2-3 Comp. 15 0.2 219 0.96 0.96 Example 2-4 Comp. 126 13.0 187 0.21 20.9 Example 2-5

(25) As apparently recognized from the above Examples, the NiZnCu-based ferrite sintered ceramics according to the present invention is excellent in temperature characteristic and DC superimposition characteristic and, therefore, suitable as a magnetic material for inductance devices.

(26) In addition, since the NiZnCu-based ferrite sintered ceramics obtained by sintering the NiZnCu-based ferrite particles according to the present invention is excellent in temperature characteristic and DC superimposition characteristic, the NiZnCu-based ferrite particles are suitable as a magnetic material for inductance devices.

(27) Further, since the NiZnCu-based ferrite sintered ceramics obtained by sintering a green sheet produced by forming the NiZnCu-based ferrite particles and a binder material into a sheet shape is excellent in temperature characteristic and DC superimposition characteristic, the green sheet is suitable as a magnetic material for inductance devices.