Transparent glass ceramics - with small thermal expansion coefficients contg hexagonal quartz mixed crystals

摘要

The ceramic has a thermal expansion coefficient 19 x 10-7/degrees C (20-300 degrees C) and a S.G. within 0.5% of starting material is prepn. from glasses contg. finely divided oxides by heat treatment pref. of compsn. (in mol. %) SiO2 45-55; Al2O3 22-27; P2O5 2.5-6.5; MgO 0-15; Li2O 5-17; ZnO 0-7; TiO2 1-5; ZrO 0-2.5; K2O or Na2O 0.3-1; As2O3 0.2-1 and TiO + ZrO2 >=2.5. The calculated content xi of components Si2O4 (x1), AlPO4 (x2), Li2Al2O4 (x3), MgAl2O4 (x4) and ZnAl2O4 (x5) comprise at least 80% of the glass and the equation 5 SIGMA xi DELTA Vi = O for coefficients DELTA V1 approx. - 10, DELTA V2 approx. -5, DELTA V3 approx. + 20, DELTA V4 approx. + 12 and + 10 = DELTA V5 20 is satisfied.