Abstract
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 B 2 O 3 and decreases 56% by doping with P 2 O 5 . Thermal expansion mismatch and microstructure non-uniformity are the proposed mechanisms responsible for the changes in strength. The effects of doping concentration of B 2 O 3 and P 2 O 5 and thermal treatment conditions on the microstructure and mechanical strength of a lithium aluminosilicate glass-ceramic material with TiO 2 and ZrO 2 were studied. The local environment around Ti and Zr correlated to the secondary phase development, such as TiZrO 4 and ZrSiO 4 , 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 B 2 O 3 and P 2 O 5 . © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.