Application of an X-Ray Microdiffractometer to a State Analysis of Low-Thermal-Expansion Porcelain and Glass Ceramics

Crystalline orientation and distribution in heat-resistant porcelain and glass ceramics containing some kinds of crystals with marked thermal anisotropy were studied with an X-ray microdiffractometer equipped with a curved position sensitive proportional counter. The surface of a porcelain plate for tableware contained predominantly crystallites of β-quartz solid solution with a little orientation. The quantity of β-quartz solid solution decreased rapidly with increasing distance from the surface, and the crystallites of indialite and enstatite with relatively even orientation increased to replace that of β-quartz solid solution. Crystallites of indialite and enstatite distributed uniformly in the interior more than 200μm from the surface. It suggests a possibility of improvement in the capability against thermal shock by reducing the crystalline size and increasing the homogeneity of the crystallite distribution in the vicinity of the surface. Almost the same X-ray microdiffraction patterns of β-eucryptite were obtained from any position of a plate of transparent glass ceramics containing β-eucryptite solid solutions as its crystalline constituent. Almost the same patterns of β-spodumene were obtained regardless of the position analyzed in a plate of white glass ceramics containing β-spodumene solid solutions. These facts indicate random orientation and uniform distribution of their crystalline constituents, which explain their superior resistance against thermal shock.