Stevens, Davis, Miller & Mosher
Solid electrolytes
 ZrO.sub.2 -Y.sub.2 O.sub.3 solid electrolytes having a high strength and an excellent deterioration property so as to be durable for a long time, comprised mainly of cubic crystal and monoclinic crystal or cubic crystal, monoclinic crystal and tetragonal crystal, wherein an average grain size of monoclinic crystal or tetragonal crystal is not greater than 2 .mu.m and a ratio of the intensity of the monoclinic (III) X-ray diffraction line to that of the cubic (200) line is 0.01-2.5. In the case of solid electrolytes comprised mainly of cubic crystal, monoclinic crystal and tetragonal crystal, the following definition is necessary. A ratio of the intensity of the tetragonal (200) X-ray diffraction line to that of the cubic (200) line is not greater than 1.0. 
NGK Insulators Ltd.
Y C Y G H
Y02P C04B Y02E G01N H01M
additional inventional additional inventional inventional
Tetsuo Syunzo Shigeo
Watanabe Mase Soejima