Effects of different aluminum sources on characteristics of β-spodumene glass-ceramics via sol-gel route

Lithium aluminosilicate glass-ceramics with β-spodumene composition were prepared by the sol-gel process from three different aluminum sources, namely, aluminum nitrate, aluminum nitrate and aluminum isopropoxide with a molar ratio of 1:1 and aluminum isopropoxide. The results show that β-eucryptite is the main crystalline phase in the sample prepared from aluminum nitrate. The main crystalline phase of samples prepared from aluminum isopropoxide or aluminum isopropoxide mixture with aluminum nitrate is β-spodumene phase. No obvious difference was observed in thermal expansion behavior in the three sets of samples. The samples sintered at 800°C with different aluminum sources have a positive coefficient of thermal expansion in the measurement temperature range from 50-750°C, while the samples sintered at 1300°C have a negative coefficient of thermal expansion. The specimens with zero thermal expansion can be obtained by controlling the sintering temperature. The microstructures of samples prepared with different aluminum sources are spherulitic crystals with a size range from 2 to 4μm.