Effects of high pressure on stability of the nanocrystalline LiAlSi2O6 phase of a glass-ceramic composite: A synchrotron X-ray diffraction study

Synchrotron X-ray diffraction studies, under pressures up to 50 GPa, have been performed on a lithium-aluminosilicate glass-ceramic composite with nanometer-sized LiAlSi2O6 crystals embedded in a host matrix. The pressure-induced evolution of X-ray diffraction patterns was followed in a diamond anvil cell on compression and decompression cycles with the aim of probing the effect of high-pressure compression on the nanocomposite structure. On the compression cycle from ambient pressure up to 20 GPa the unit cell volume of the LiAlSi2O6 phase decreased by about 22%. The diffraction patterns also revealed the presence, at high pressures, of the ZrTiO4 phase that was nucleated in the matrix prior to the crystallization of the main LiAlSi2O6 phase. After quenching from 50 GPa to close to ambient conditions the diffraction pattern indicated that the high-pressure phase was retained to some extent although the decompressed structure still carried the signature of the initial ambient LiAlSi2O6 phase. A Birch-Murnaghan fit of the unit cell volume as a function of pressure yielded a zero pressure bulk modulus K0=71±2GPa and its pressure derivative K0′=4.4±0.6GPa for the nanocrystalline phase.