Zn2+- Controlled Crystallization and Microstructure in K-Li-Mg-B-Si-Al-F Glass

Text: The crystallization of (9-X) K2O-1Li(2)O-12MgO-10B(2)O(3)-40SiO(2)-16Al(2)O(3)-12MgF(2)-X PbO/BaO/ZnO (X=0./5) composition (wt.%) were studied by means of dilatometry. DSC, XRD, SEM and microhardness analysis. Density of base K-Li-Mg-B-Si-Al-F glass (2.59 g.cm(-3)) is found to be increased on addition of the network modifier. oxides PbO, BaO and ZnO content. Addition of Pb2+ Ba2+ and Zn2+ furthermore increased the glass transition temperature (T-g). A characteristic exothermic hump is found to be appeared in DSC thermograph at the temperature range 800-950 degrees C; and that is ascribed to the formation of crystalline phase fluorophlogopite mica, KMg3(AlSi3O10)F-2. Opaque glass-ceramics were prepared from K-Li-Mg-B-Si-Al-F glasses (with and without containing PbO, BaO and ZnO content) by controlled heat-treatment at 1000 degrees C. Interlocked type microstructure combined of flake like fluorophlogopite mica crystals is obtained in ZnO-containing K-Li-Mg-B-Si-Al-F glass-ceramic; and such microstructural pattern is ascribed to cause large thermal-expansion (>11.5x10(-6)/K, 50-800 degrees C). Vickers Microhardness of base glass-ceramic (5.12 GPa) is increased when contains ZnO (5.26 GPa). ZnO-containing boroaluminosilicate glass-ceramic is, hence, considered with potential interest as they can exhibit the microcrack resistivity in high temperature recycling operation (like SOFC).