ZINC OXIDE VARISTOR AND METHOD FOR MANUFACTURING SAME

• US 20190322588A1
• Filed: 12/07/2017
• Published: 10/24/2019
• Est. Priority Date: 12/07/2016
• Status: Active Grant

• Current Assignee: KOA Corporation
• Original Assignee: JFE Mineral Company Limited (JFE Holdings Incorporated), KOA Corporation
• Inventors: GOMI, Yoji, IGUCHI, Kenichi, UDAGAWA, Etsurou, ECHIZENYA, Yuko, NAKATA, Yoshimi
• Granted Patent: US 11,370,712 B2
• Time in Patent Office: Days
• CPC Class Codes: C01G 9/02 Oxides; Hydroxides
• CPC Class Codes: C01P 2002/60 Compounds characterised by their crystallite size
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/51 Particles with a specific particle size distribution
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/10 Solid density
• CPC Class Codes: C01P 2006/11 Powder tap density
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3262 Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
• CPC Class Codes: C04B 2235/3275 Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/3279 Nickel oxides, nickalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3284 Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3286 Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/3298 Bismuth oxides, bismuthates or oxide forming salts thereof, e.g. zinc bismuthate
• CPC Class Codes: C04B 2235/3409 Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
• CPC Class Codes: C04B 2235/5454 nanometer sized, i.e. below 100 nm
• CPC Class Codes: C04B 2235/549 the particle size being expressed by crystallite size or primary particle size
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/781 : Nanograined materials, i.e. having grain sizes below 100 nm
• CPC Class Codes: C04B 2235/785 : Submicron sized grains, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/85 : Intergranular or grain boundary phases
• CPC Class Codes: C04B 2235/96 : Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9607 : Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 35/453 : based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
• CPC Class Codes: C04B 35/62675 : characterised by the treatment temperature
• CPC Class Codes: H01B 1/08 : oxides
• CPC Class Codes: H01C 7/112 : ZnO type
• CPC Class Codes: H01C 7/12 : Overvoltage protection resistors series resistors structurally associated with spark gaps H01T1/16

Abstract

Focus is on zinc oxide itself, which is a base material for a zinc oxide varistor (laminated varistor), wherein specified quantities of additives are added to a zinc oxide powder having a crystallite size of 20 to 50 nm, grain diameter of 15 to 60 nm found using the specific surface area BET method, untamped density of 0.38 to 0.50 g/cm³, and tap density of 0.50 to 1.00 g/cm³. This allows securing of uniformity, high compactness, and high electrical conductivity of a zinc oxide sintered body, and provision of a zinc oxide varistor having high surge resistance.

Claims

1. A zinc oxide varistor, comprising zinc oxide (ZnO) as a main component, one or more kinds of additives selected as a grain boundary forming component from a group including bismuth (Bi) and praseodymium (Pr), and one or more kinds of additives selected as a transition metal element from a group including cobalt (Co), manganese (Mn) and nickel (Ni);

wherein the zinc oxide has a crystallite size of 20 to 50 nm found by X-ray diffraction, grain diameter of 15 to 60 nm found using a specific surface area BET method, untamped density of 0.38 to 0.50 g/cm³, and tap density of 0.50 to 1.00 g/cm³.

3. The zinc oxide varistor according to claim 1, wherein crystallite size when powder of the zinc oxide is sintered at 1000°

C. is 70 to 1200 nm, and crystallite size when sintered at 1150°

C. is 75 to 170 nm.

4. The zinc oxide varistor according to claim 3, wherein increasing rate of the crystallite size of the zinc oxide by sintering within the range of 1000°

C. and 1150°

C. is 10% or less.

5. The zinc oxide varistor according to claim 1, wherein one or more kinds of donor elements including aluminum (Al), boron (B), and gallium (Ga) is further added.

2. A zinc oxide varistor, comprising zinc oxide (ZnO) as a main component, one or more kinds of additives selected as a grain boundary forming component from a group including bismuth (Bi) and praseodymium (Pr), and one or more kinds of additives selected as a transition metal element from a group including cobalt (Co), manganese (Mn) and nickel (Ni);

wherein the zinc oxide has median diameter of 30 to 60 nm found using a dynamic scattering method, cumulant diameter of 40 to 82 nm, and cumulant polydispersity index of 0.05 to 0.20.

10. The zinc oxide varistor according to claim 2, wherein crystallite size when powder of the zinc oxide is sintered at 1000°

C. is 70 to 1200 nm, and crystallite size when sintered at 1150°

C. is 75 to 170 nm.

11. The zinc oxide varistor according to claim 10, wherein increasing rate of the crystallite size of the zinc oxide by sintering within the range of 1000°

C. and 1150°

C. is 10% or less.

12. The zinc oxide varistor according to claim 2, wherein one or more kinds of donor elements including aluminum (Al), boron (B), and gallium (Ga) is further added.

6. A manufacturing method of a zinc oxide varistor, comprising the steps of:

manufacturing basic zinc carbonate slurry that is a first precursor of zinc oxide (ZnO) powder;

obtaining from the first precursor a dried powder of basic zinc carbonate that is a second precursor of zinc oxide (ZnO) powder;

obtaining zinc oxide (ZnO) through heat treatment of the second precursor;

manufacturing a mixed material resulting from adding a predetermined additive to the zinc oxide (ZnO); and

forming a varistor element for a zinc oxide varistor from the mixed material.

7. The manufacturing method of a zinc oxide varistor according to claim 6, wherein the zinc oxide varistor comprises zinc oxide (ZnO) as a main component, one or more kinds of additives selected as a grain boundary forming component from a group including bismuth (Bi) and praseodymium (Pr), and one or more kinds of additives selected as a transition metal element from a group including cobalt (Co), manganese (Mn) and nickel (Ni);

and

the zinc oxide has a crystallite size of 20 to 50 nm found by X-ray diffraction, grain diameter of 15 to 60 nm found using the specific surface area BET method, untamped density of 0.38 to 0.50 g/cm³, and tap density of 0.50 to 1.00 g/cm³.

8. The manufacturing method of a zinc oxide varistor according to claim 6, wherein the zinc oxide varistor comprises zinc oxide (ZnO) as a main component, one or more kinds of additives selected as a grain boundary forming component from a group including bismuth (Bi) and praseodymium (Pr), and one or more kinds of additives selected as a transition metal element from a group including cobalt (Co), manganese (Mn) and nickel (Ni);

and

the zinc oxide has median diameter of 30 to 60 nm found using a dynamic scattering method, cumulant diameter of 40 to 82 nm, and cumulant polydispersity index of 0.05 to 0.20.

9. The manufacturing method of a zinc oxide varistor according to claim 7, wherein one or more kinds of donor elements including aluminum (Al), boron (B), and gallium (Ga) is further added.

13. The manufacturing method of a zinc oxide varistor according to claim 8, wherein one or more kinds of donor elements including aluminum (Al), boron (B), and gallium (Ga) is further added.