Abstract
Glasses in the Na2O–Ba0–A12O3‐Si02 system, nucleated with TiO2, were heat‐treated to effect controlled crystallization. Resulting materials consisted of a dense, micro‐crystalline mixture of nepheline (Na20–A12O3‐2SiO2) and barium feldspar (BaO‐A12O3‐2Si02) in a glassy matrix. Thermal expansion coefficients (O° to 300° C) of these bodies ranged from 75 to 125 × 10 –7/°C. Glazes in the Na2O‐CaO‐PbO‐B2O2‐A1203‐SiO2 system having expansion coefficients of about 40 to 80 × 10 ‐7/0°C were applied to the glass‐ceramics. On firing, the glazes matured well and reacted with the bodies to form interlocking crystals at the interface. This interfacial region was investigated using several instrumental techniques, and the crystals were identified as plagioclase feldspar. Applying these compressive glazes resulted in modular of rupture up to five times that of the initial glass‐ceramic. Calculated strengths correlated well with experimental values.
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