Champion Spark Plug Company

Cooper Indusries, Inc.

Terrence K Brog

William R Manning

A method for producing a ceramic is disclosed. The method involves comminuting a batch composed of from 6 to 95 percent of particulate ZrO.sub.2 and from 5 to 94 percent of particulate Al.sub.2 O.sub.3. A part of the particulate ZrO.sub.2 is in a metastable tetragonal crystal structure, for example, as a consequence of 3.sup.m/o of Y.sub.2 O.sub.3 dissolved therein and a part has a monoclinic crystal structure. The comminuted batch is compacted into a shape, and the shape is fired. The degree of comminution of the batch, the firing conditions and the proportions of stabilized and monoclinic ZrO.sub.2 in the batch are controlled to produce a dense, gas impervious ceramic which contains both metastable tatragonal and monoclinic ZrO.sub.2, and in such proportions that the ceramic has improved strength by comparison with an otherwise identical ceramic wherein all of the ZrO.sub.2 is in either a metastable tetragonal or a monoclinic crystal structure. Also disclosed is a method where the particulate alumina can be an alumina-chromia solid solution containing up to 50.sup.m/o of chromia. In another embodiment, a ceramic article is disclosed. The article is composed of from 6 to 95 percent of particulate ZrO.sub.2, from 5 to 94 percent of particulate Al.sub.2 O.sub.3, from 1/4 to 33/4 percent of MnO.sub.2 and from 1/4 to 33/4 percent of TiO.sub.2 .

Alumina-zirconia ceramic

A ceramic article is disclosed. The article is composed of from 6 to 50 percent of particulate ZrO.sub.2 having an ultimate particle size less than 2 .mu.m, from 50 to 94 percent of particulate Al.sub.2 O.sub.3, from 1/4 to 3 percent of MnO.sub.2 and from 1/4 to 3 percent of TiO.sub.2.

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Littleton, CO, United States of America

Terrence K Brog