Refractory glass ceramics

Abstract

A formation of internally nucleated glass ceramics articles that can be heated in the 1350-1450° C. range for extended periods of time without significant deformation or change in shape is disclosed. The predominant crystal phase of these glass ceramics is celsian (BaAl 2 Si 2 O 8 ) or its strontium equivalent (SrAl 2 Si 2 O 8 ), or solid solutions or mixtures of these compositions, all belonging to the feldspar mineral group.

1 . A method of making a glass ceramic article which comprises the steps of:
 melting a batch of raw materials including at least one nucleating agent to a temperature of 1550° C. to 1700° C. for a period of time sufficient to achieve a molten homogeneous melt;   forming into a desired shape, a glass article from said melt;   annealing the glass article at a temperature in the range of 700° C. to 850° C.   heat treating the glass article at a temperature of 800° C. to 900° C. for a period of time sufficient for homogeneous dispersion and development of nuclei from the nucleating agent;   crystallizing the glass at a temperature in the range of 950° C. to 1450° C. for a time sufficient to achieve maximum crystallinity thereby transforming the glass article into a glass ceramic article;   cooling the glass ceramic article; and   whereby said glass ceramic article does not deform or change in shape when heated within the range of 1250° C.-1450° C.   
     
     
         2 . The method of making a glass ceramic article of  claim 1  whereby said glass ceramic article has a CTE in the range of 30−55×10 −7 /° C. in the temperature range 25-1000° C.