# US 5,702,998 A · Sintered ceramic body for a spark plug insulator and method of sintering the same

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,702,998 A
- Document ID: US5702998A
- Status: Granted
- Kind: A
- Application number: 08/285,832
- Filed: 1994-08-04
- Granted: 1997-12-30
- Earliest claimed: 1990-10-22
- Assignees: Ngk Spark Plug Co., Ltd.
- Inventors: Makoto Sugimoto; Mamoru Musasa; Hiroyuki Tanabe; Masahiro Konishi
- Web page: https://patentgrep.com/patent/US5702998A

## CPC

- H01T 13/38: Selection of materials for insulation
- C04B 35/597: based on silicon oxynitride, {e.g. SIALONS}
- H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H)
- 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

## Abstract

In a spark plug insulator having a sintered ceramic body, the ceramic body has silicon nitride (Si.sub.3 N.sub.4), aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3), the sum of the weight of aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3) to silicon nitride (Si.sub.3 N.sub.4) is in the range of 0.093.about.1.439. Typically, the additive is represented by the group consisting of yttrium oxide (Y.sub.2 O.sub.3), calcium oxide (CaO), lanthanum oxide (La.sub.2 O.sub.3), magnesia (MgO), cerium oxide (SrO), barium oxide (BaO) and neodymium (Nd.sub.2 O.sub.3). The percentage by weight of the sintering additive ranges from 0.3% to 15.0% of the total weight of the silicon nitride (Si.sub.3 N.sub.4), aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3).

## Claims

### Claim 1

A sintered ceramic spark plug insulator body consisting essentially of silicon nitride (Si.sub.3 N.sub.4), aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3), the ratio of the sum of the weight of aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3) to silicon nitride (Si.sub.3 N.sub.4) being in the range 0.093-1.439 and at least one sintering additive selected from the group consisting of yttrium oxide (Y.sub.2 O.sub.3), calcium oxide (CaO), lanthanum oxide (La.sub.2 O.sub.3), magnesia (MgO), cerium oxide (CeO.sub.2), scandium oxide (Sc.sub.2 O.sub.3), strontium oxide (SrO), barium oxide (BaO) and neodymium (Nd.sub.2 O.sub.3), the weight percentage of the sintering additive being in the range from 0.3 to 15.0 of the total weight of the silicon nitride (Si.sub.3 N.sub.4), aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3), said sintered ceramic body having an electrical resistance of 50 M/.OMEGA. or more at 700.degree. C., the composition of said spark plug insulator body being within the area bounded by the straight lines connected points A, C, E, J, T, R and A shown in the three-component or triaxial diagram of FIG. 1, said three component diagram being made up of the compounds (Si.sub.3 N.sub.4), aluminum nitride (AlN) and alumina (Al.sub.2 O.sub.3).