# US 11,299,427 B2 · Magnesium oxide based dielectric ceramics with ultrahigh dielectric breakdown strength and its preparation method

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- Number: US 11,299,427 B2
- Document ID: US11299427B2
- Status: Granted
- Kind: B2
- Application number: 16/822,950
- Filed: 2020-03-18
- Published: 2020-10-01
- Granted: 2022-04-12
- Earliest claimed: 2019-03-26
- Assignees: Shanghai Institute of Ceramics, Chinese Academy of Sciences
- Applicants: Shanghai Institute of Ceramics, Chinese Academy of Sciences
- Inventors: Xianlin Dong; Chi Zhang; Ying Chen
- Web page: https://patentgrep.com/patent/US11299427B2

## CPC

- C04B 35/053: Fine ceramics
- C04B 35/62655: {Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying}
- C04B 35/63416: {Polyvinylalcohols [PVA]; Polyvinylacetates}
- C04B 35/6342: {Polyvinylacetals, e.g. polyvinylbutyral [PVB]}
- C04B 35/63476: {Phenol-formaldehyde condensation polymers}
- C04B 35/638: Removal thereof
- C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F})
- H01B 3/12: ceramics
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3222: Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
- C04B 2235/44: Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
- C04B 2235/442: Carbonates
- C04B 2235/444: Halide containing anions, e.g. bromide, iodate, chlorite
- C04B 2235/449: Organic acids, e.g. EDTA, citrate, acetate, oxalate
- C04B 2235/6562: Heating rate
- C04B 2235/6567: Treatment time
- C04B 2235/763: Spinel structure AB2O4
- C04B 2235/784: Monomodal
- C04B 2235/786: Micrometer sized grains, i.e. from 1 to 100 micron
- C04B 2235/80: Phases present in the sintered or melt-cast ceramic products other than the main phase
- C04B 2235/87: Grain boundary phases intentionally being absent
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE
- H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K})

## Abstract

The present application relates to a magnesium oxide based dielectric ceramics with ultrahigh dielectric breakdown strength and a preparation method thereof. The composition of the magnesium oxide based dielectric ceramic material comprises: (1−x)MgO—xAl2O3, wherein 0<x≤0.12 and x is a mole percentage. The material has a specific composite structure with magnesium aluminate spinel acting as a second phase surrounding a principal crystalline phase, MgO.

## Claims

### Claim 1

A magnesium oxide based dielectric ceramic material, having a composition of (1−x)MgO—xAl2O3, wherein 0.08≤x≤0.1 and x is a mole percentage, and having a composite structure with magnesium aluminate spinel acting as a second phase surrounding a principal crystalline phase, MgO;
wherein the magnesium oxide based dielectric ceramic material has a dielectric breakdown strength of 111.5 to 126.4 kV/mm and a surface flashover strength of 74.3 to 78.7 kV/cm; and
wherein the magnesium oxide based dielectric ceramic material is prepared by a method including:
weighing and mixing magnesia and alumina according to the composition of the magnesium oxide based dielectric ceramic material to obtain mixed powders, wherein the magnesia is light-burnt magnesia obtained by calcining magnesium source at a temperature of 800 to 1,000° C. for a period of 2 to 6 hours;
preparing a green body from the mixed powders; and
sintering the green body at a temperature of 1,500 to 1,550° C. for a period of 1 to 3 hours to obtain the magnesium oxide based dielectric ceramic material having the composition of (1−x)MgO—xAl2O3.

### Claim 2 (depends on 1)

The magnesium oxide based dielectric ceramic material according to claim 1, wherein the average grain size of the principal crystalline phase is 1 to 5 μm.