Ngk Spark Plug Company, Limited

Takeshi Kitano

Nobuhiro Hayakawa

Hiroyuki Ishiguro

Yutaka Adachi

As a solid electrolyte suitable for use in oxygen sensors a partially stabilized zirconia, which essentially consists of 4.5-6.0 mol % of Y.sub.2 O.sub.3 and the balance of ZrO.sub.2 and is constituted of tetragonal and cubic crystals, is produced by using a coprecipitated powder of a solid solution of ZrO.sub.2 and Y.sub.2 O.sub.3 as the raw material and performing sintering of a green body at a temperature not higher than 1500.degree. C. The ZrO.sub.2 -Y.sub.2 O.sub.3 powder has a mean particle size not larger than 1 .mu.m and a specific surface area in the range from 2.5 to 7 m.sup.2 /g and is required to be not more than 0.2 wt % in the content of unwanted SiO.sub.2 so that the sintered solid electrolyte may be as low as possible in the content of SiO.sub.2. The obtained solid electrolyte has good mechanical properties and exhibits sufficiently high withstand voltage.

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Aichi, Japan

Takeshi Kitano