Effects of B2O3 and P2O5 doping on the microstructure evolution and mechanical strength in a lithium aluminosilicate glass–ceramic material with TiO2 and ZrO2

During the devitrification process, the coordination number of Ti changes from 4 and 5 to 6; and the coordination number of Zr changes from 6 to 8 in a lithium aluminosilicate glass–ceramic material. The flexural strength of the glass–ceramics strongly depends on the composition of additives. The strength of a well-crystallized sample increases 45% by doping with B2O3 and decreases 56% by doping with P2O5. Thermal expansion mismatch and microstructure non-uniformity are the proposed mechanisms responsible for the changes in strength. The effects of doping concentration of B2O3 and P2O5 and thermal treatment conditions on the microstructure and mechanical strength of a lithium aluminosilicate glass–ceramic material with TiO2 and ZrO2 were studied. The local environment around Ti and Zr correlated to the secondary phase development, such as TiZrO4 and ZrSiO4, during the crystallization process was observed by X-ray absorption near edge structure. The electronic structure of each peak in the X-ray absorption near edge spectra was also assigned in terms of phase evolutions. The phase transformation temperature of β-quartz solid solutions to β-spodumene solid solutions is decreased for about 100 °C by adding B2O3 and P2O5.