Youngʹs moduli and microhardness of glass–ceramics in the system MgO/Al2O3/TiO2/ZrO2/SiO2 containing quartz nanocrystals

Glasses with the compositions (60.2 − 2x)SiO2·(16.2 + x)Al2O3·(16.2 + x)MgO·3.7TiO2·3.7ZrO2 (x = 0, 2.3, 4.65, 6.95, 8.1 and 9.25) were annealed at temperatures in the range from 800 to 1100 °C. This led to the precipitation of high- or low-quartz solid solution nanocrystals, magnesium aluminosilicate, mullite and spinel, depending on temperature and chemical composition. Large SiO2-concentration (x = 0) led to the crystallization of magnesium aluminosilicate as the main crystalline phase. Smaller SiO2-concentrations led to the crystallization of quartz. If these samples were annealed at temperatures ≤1000 °C, high-quartz solid solutions were formed which did not transfer to the low temperature modification during cooling. The microhardness of the glasses were in the range from 7 to 8.5 GPa, while the Youngʹs moduli were 105 to 120 GPa. After annealing, the microhardness was up to 12.3 GPa and the Youngʹs moduli up to 152 GPa.