Phase Transformations upon Formation of Transparent Lithium Alumosilicate Glass-Ceramics Nucleated by Yttrium Niobates

Phase transformations in the lithium aluminosilicate glass nucleated by a mixture of yttrium and niobium oxides doped with cobalt ions were studied for development multifunctional transparent glass-ceramics. Initial glass-ceramics obtained isothermal heat-treatments at 700–900 °C contain YNbO4 nanocrystals distorted tetragonal structure. In samples heated 1000 above, monoclinic features are observed. High-temperature X-ray diffraction technique clarifies mechanism orthoniobate formation, which occurs not upon high-temperature above 900 but cooling after such heat-treatments, when structure undergo second-order transformation ~550 °C. Lithium solid solutions (ss) β-quartz main crystalline phase prepared temperature range 800–1000 These structural confirmed Raman spectroscopy illustrated SEM study. The absorption spectrum material changes only crystallization ss due to entering Co2+ into this mainly octahedral coordination, substituting Li+ ions. At °C, coordination tetrahedral one. Transparent have thermal expansion coefficient about 10 × 10−7 K−1.