Ceramic Compositions Having Negative Linear Thermal Expansion

Compositions having negative linear thermal expansions ranging from 0 to –0.38% have been obtained in two areas of the system lithia‐alumina‐silica. Petrographic and X‐ray examinations indicate the presence of three principal crystalline phases, each of which is a solid solution: β ‐eucryptite, β ‐spodumene, and an unidentified quartzlike phase. All compositions were prepared from lithium carbonate, clay, flint, and alumina. Some compositions have been prepared which, for all practical purposes, exhibit no change in length when heated from room temperature to as high as 600°C. Some of these compositions have excellent thermal endurance, withstanding repeated quenchings from a temperature of 1100°C. into water at room temperature.