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Abstract

This invention relates to processes for preparing ceramic articles. One process involves taking a potassium exchanged zeolite, the zeolite characterized in that it has a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of 3.5 to about 7.5, and calcining it at a temperature of about 900.degree. to about 1100.degree. C. for a time sufficient to collapse the zeolite framework and provide an amorphous powder. Next, the amorphous powder is formed into a shaped article and the article is sintered at a temperature of about 1150.degree. to about 1400.degree. C. for a time of about 0.5 to about 12 hours to give a ceramic article whose principal crystalline phase is tetragonal leucite, is substantially crack free, and has less than 5% porosity. When the zeolite is exchanged with cesium, one obtains a ceramic article whose principal crystalline phase is pollucite, when a rubidium exchanged zeolite is used one obtains a ceramic article whose principal crystalline phase is rubidium leucite, and when a potassium/cesium exchanged zeolite is used one obtains a ceramic article having as its principal crystalline phase a leucite/pollucite solid solution. The addition of pollucite to the leucite article provides a ceramic article whose thermal expansion coefficient can be varied from about 2.times.10.sup.-6 to about 27.times.10.sup.-60 C.sup.-1 as measured over the range 50.degree.-700.degree. C. This invention also relates to this leucite/pollucite ceramic article.

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First Claim