The effect of Zn/Ti ratio on crystallization behavior of ZMAS(ZnO-MgO-Al2O3–SiO2) glass ceramics

In this study, the basic composition is 15%ZnO, 20.48%MgO, 19.90%Al2O3, 38.62%SiO2, and three compositions were prepared by reducing the weight of ZnO in the composition and adding TiO2 internally to the system in order to obtain different Zn/Ti ratios. The prepared powder mixtures were named as ZMAS-1, ZMAS-2 and ZMAS-3. ZMAS-1 contains 15%ZnO, 20.48%MgO, 19.90%Al2O3, 38.62%SiO2, 5%TiO2, %1Sb2O3 by weight; ZMAS-2 contains, 12.5%ZnO, 20.48MgO, 19.90%Al2O3, 38.62%SiO2, 7.5%TiO2, %1Sb2O3 and ZMAS-3 contains 10%ZnO, 20.48MgO, 19.90%Al2O3, 38,62%SiO2, 10%TiO2, %1Sb2O3 by weight. ZMAS powder compositions were obtained by weighing the stoichiometrically determined pure raw materials in the spinel formation region of the MAS triple equilibrium diagram. The homogenization process was performed in a ball mill in a dry environment for 12 hours, and after the process, ZMAS powder mixtures was put into alumina, crucibles and melted at 1450- 1500°C of 3,5 hours. The molten glass was shaped by casting into a graphite mold and immediately after this process, it was kept in an annealing furnace at 600°C for 1 hour. XRD for phase analysis and DTA analysis for determination of thermal properties were applied to the produced ZMAS-based glasses by performing crushing-grinding-sieving processes. ZMAS glass ceramics were obtained by sintering the produced ZMAS glasses at the temperatures and times determined by DTA analysis (800°C -950°C 1-5 hours) at a heating, rate of, 5°C /min by applying a single-stage heat treatment to gain strength; XRD and SEM analyses were conducted. According to the XRD analyzes carried out, it was determined that the ZMAS-based glass ceramics consisted of gahnite, enstatite and quartz phases. Microhardness, density and dielectric properties of ZMAS-based glass ceramics were also investigated. The hardness, values measured for ZMAS glass ceramics, vary between 548-1020 HV0,05, depending, on the crystallization temperature, and time. Density values determined by Archimedes method are between 2.13-3.05 g/cm3. It has been determined that with the decrease of the Zn/Ti ratio, the dielectric constant tends to decrease and the dielectric loss to increase.