Crystal Growth Behavior, Nanometer Microstructure, and Mechanical Properties of Diopside-Based Glass-Ceramics

In this study, to increase the light transmittance of diopside type crystallized glass, crystals with size of less than 100 nm, which is smaller than the visible light wavelength, were generated in the specimen. For this purpose, the so-called two-step process encompassing heat treatment at the nucleation temperature followed by heating the crystal at the crystal growth temperature was employed. The crystallization behavior of the prepared specimen was studied and the optical and mechanical properties were investigated according to the heat treatment conditions. The glass used in the experiment was CaO-MgO-2SiO₂, which is a stoichiometric composition of diopside crystals. Heat-treating temperatures for nucleation and crystal growth were determined by a nonisothermal thermal analysis using Differential Thermal Analysis (DTA). The most suitable heattreating conditions were nucleation at 761 °C/6 h and crystal growth at 880 °C/1 h. The generated diopside crystal size was below 100 nm on average and the light transmittance was as high as ~75% for most of the specimens and the parent glass specimen showed higher light transmittance than that of conventional commercialized semitransparent crystallized glass products. The bending strength of diopside-based glass-ceramics was 30 MPa and the fracture energy was 1.56 N/mm. The Avrami constant calculated from the Kissinger equation and the Augis-Bennett equation was 1.38 and the activation energy was 355.63 kJ/mol, and these value indicate surface crystallization behavior.