Effect of TiO2 doping on crystallization, microstructure and dielectric properties of CBS glass-ceramics

Abstract

In this study, calcium borosilicate (CaO-B2O3-SiO2, CBS) glass-ceramics were fabricated using chemically pure CaO, SiO2, and B2O3 as raw materials. Differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and electrical measurements were conducted to explore the effect of titanium dioxide (TiO2) doping on crystallization, microstructure, and dielectric properties of CBS glass-ceramics. Furthermore, the influence of sintering temperature and sintering schemes on crystalline phases of CBS glass-ceramics was systematically investigated. Results showed that the increase of TiO2 content led to the reduction in sintering temperature of CBS glass-ceramics and promoted the precipitation of wollastonite crystal phase. For instance, with the increase of content of TiO2 from 0 to 3 wt%, transition temperature and crystallization temperature were reduced by 12.9 and 27.6 °C, respectively. However, excessive TiO2 affected the precipitation of wollastonite crystal phase, destroyed crystal structure, and damaged close arrangement of crystal grains. Moreover, higher TiO2 content was found to weaken dielectric properties of CBS glass-ceramics. In this study, the best molar ratio of ingredients, meeting that of ideal target material, is n(Ca): n(Si): n(B) = 1:1:0.6, with doping mass fraction of 2 wt% of TiO2. After optimal sintering procedure, dielectric constant of the best sample was found to be 1.4 (1 MHz), 1.3 (10 MHz), and dielectric loss was 3.9 × 10−3 (1 MHz) and 3.8 × 10−3 (10 MHz).