Effects of CeO2 nanoparticles and annealing temperature on the microwave dielectric properties of MgTiO3 ceramics

MgTiO3 (MTO) ceramics have been prepared by the conventional solid-state reaction method. The effects of CeO2 nanoparticles up to 1.5 wt% as a sintering aid and annealing temperature on the crystal structure, microstructure and microwave dielectric properties of MTO ceramics were investigated. It is found that the addition of CeO2 nanoparticles to the MTO ceramics leads to improvement in the relative density, reduction in sintering temperature. However, Q×fo values are found to decrease marginally. The driving forces for the improved sintering process are the large surface energy of CeO2 nanoparticles and their defect energy, which are activated during the sintering process. The addition of CeO2 nanoparticles does not change the dielectric constant (εr), and the unloaded quality factor (Qu) but the τf values are altered significantly. The annealing temperatures of the pure MTO ceramics and MTO+xCeO2 (x=0.5, 1.0 and 1.5 wt%) were optimized. The samples annealed at 1100 °C for 48 h exhibit the best microwave dielectric properties. The maximum value of Q×fo for the pure MTO was achieved by sintering at1400 °C and significantly such maximum value was achieved in x=0.5 wt% sample by sintering at 1300 °C itself. The values of Q×fo are in the range of 52250–140800 GHz. Pure MTO ceramics sintered at 1400 °C and annealed at 1100 °C for 48 h exhibit the best microwave dielectric properties (εr=17.21, Q׃o=165500 GHz). The observed results are correlated to the reduction in oxygen vacancies, relaxation of strain during annealing, increase in grain size and relative densities.