Glass‐ceramic nanospheres of molar composition 0.83 SiO2 · 0.17 TiO2 are produced by the sol‐gel spray‐drying method followed by controlled heat treatments up to 1200 °C. TiO2(B) and anatase nanocrystals are precipitated in the glassy matrix: the latter phase gradually predominates with increasing ceramization temperature and time, in parallel to an overall increase in crystal sizes. The nanospheres exhibit evident photocatalytic activity under UV‐A irradiation, especially at annealing stages involving a comparatively higher amount of TiO2(B) and smaller crystals. The occurrence of TiO2(B) in this simplified binary glass‐ceramic material underlines the key role of this phase in the dynamics of crystallizing TiO2‐bearing silicate melts.
Quartz solid solution crystals of six different compositions were obtained from crystallization of glass powders belonging to the Li2O–Al2O3‐SiO2 (LAS) system. They were analyzed in situ by laboratory‐based X‐ray diffraction down to cryogenic temperatures (−190°C). Temperature‐resolved analysis of their lattice parameters allowed determination of the critical inversion temperature Tc in these materials, marking the displacive phase transition from a high‐quartz‐ to a low‐quartz‐like lattice. Integrating available data from other literature sources, an updated phase diagram for the occurrence of high and low quartz solid solution phases is provided for the LAS system; these data are expected to support future development of functional materials relying on these crystalline phases.
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