Crystallization Behavior and Optical Properties of Glass-Ceramics Containing Nano-Diopside Crystals

Abstract

Diopside is a ceramic material with excellent properties including a low dielectric constant, high thermal conductivity, low sintering temperature below 1000 °C, and high mechanical strength. It has been applied to wireless and optical communications, substrates for touch panels, lenses for UV-LED, building materials, and so on. In this study, glass-ceramics containing nano-sized diopside crystals were fabricated, and their transmittance at visible light and photoluminescence were evaluated. In particular, TiO2 was added as a nucleating agent to suppress the surface crystallization phenomenon and Mn was used as a dopant to emit red light. The glass-ceramics were prepared by heat treatment at a temperature lower than the maximum crystal growth temperature (TP) calculated from the non-isothermal analysis method using differential thermal analysis (DTA) for the formation of nano-sized crystals. For glass containing 20 wt% of TiO2, the Avrami constant was calculated to be 2.23 and the activation energy required for crystal growth to be 549 kJ/mol, reflecting typical bulk crystallization behavior. Glass-ceramics with high light transmittance up to 70% were obtained by inducing the bulk crystallization behavior, and the diopside crystal size was less than 10 nm, which was equal to or higher than that of commercialized transparent glass-ceramic products. Glass-ceramic specimens doped with Mn showed luminescence of 736∼766 nm wavelength at excitation light of 365 nm wavelength. The emission peak intensity increased with the amount of dopant added, but gradually decreased with increasing crystallinity of the diopside phase.