Transparent, high strain point spinel glass-ceramics

Transparent, refractory glass-ceramics based on 10 nm crystals of spinel solid solution in a highly siliceous residual glass can be produced from compositions in the SiO2-Al2O3-ZnO-MgO-TiO2-ZrO2 system. The glass-ceramics possess excellent chemical durability as well as thermal expansion coefficients of 35-40 x 10(-7)/degrees C and strain point temperatures of over 900 degrees C. Titania serves as both an extremely effective nucleating agent in these glasses and as an integral component of the spinel crystals. The materials are designed such that fluxes in the glass partition into the spinel crystals during the crystallization process, leaving a continuous residual glass very high in silica. The strain points of the resultant glass-ceramics approach those of vitreous silica and quartz materials which require significantly more expensive manufacturing processes. These glass-ceramics are excellent substrate candidates for high temperature, high quality polysilicon thin films. Potential products include solar cells and active matrix liquid crystal displays. (C) 1999 Elsevier Science B.V. All rights reserved.