Enhanced quality factor of wollastonite (0.9Ca0.9Mg0.1SiO3-0.1CaMgSi2O6) glass-ceramics by heat-treatment method

The effects of different heat-treatment methods on the microwave dielectric properties of wollastonite (0.9Ca(0.9)Mg(0.1)SiO(3)-0.1CaMgSi(2)O(6)) glass-ceramics were investigated. The glass powders were prepared by direct and step quenching. Single-phase p-wollastonite was obtained for specimens heat-treated at 900 degrees C for 3 h from glass powders prepared by step quenching, and these had a higher quality factor (Of) than specimens prepared by direct quenching. To increase the degree of crystallization, the step-quenched glass powders were heat-treated in two steps, for nucleation and then crystal growth. Increasing the holding time at the nucleation temperature (T-n, 725 degrees C), lead to an increase in the degree of crystallization and in Qf with a value of 72,000 GHz obtained for specimens heat-treated at 725 degrees C for 7 h and crystallized at 900 degrees C for 3 h. The dependence of the dielectric constant (K) and of the temperature coefficient of resonant frequency (TCF) on the crystallization behaviour was also investigated. (C) 2015 Elsevier Ltd. All rights reserved.