Effect of calcination time and temperature to the properties of CaCu3Ti4O12 using enhanced microwave processing

Calcium copper titanate, CaCu3Ti4O12 (CCTO) is an electroceramic in perovskite family that had received much attention due to its high dielectric constant. However, its high dielectric loss makes it lack of performing in energy. In order to overcome the problem, enhanced microwave processing is one of the techniques that are used to improve the overall process and product quality efficiency. The objectives of this study are to investigate the effect of calcination time and temperature to the properties of CCTO by using enhanced microwave processing. A microwave susceptor crucible has been synthesised by using the silicon carbide (SiC) and feldspar as raw materials in weight percentage ratio 80:20 by using conventional processing. The powder form of three raw materials which are calcium carbonate (CaCO3), copper oxide (CuO) and titanium oxide (TiO2) have been weighed according to the stoichiometric ratio to form pure CCTO. The mixed powder was ball milled for 24 hours using wet mixing. The mixed powder was calcined in different time duration (1h, 3h, 5h, 7h and 9h) at 500℃ and different temperature (500℃, 600℃, 700℃, 800℃ and 900℃) for an hour by using enhanced microwave processing. The calcined powder has been pelleted and sintered at 1040℃ for 10 hours by using conventional processing. This study is focused on the phase formation of calcined powder and sintered pellet, surface morphology and the dielectric properties of the sintered pellets. Phase formation was analysed by using X-Ray Diffraction (XRD). The XRD results had shown that the phase formation of CCTO is successfully obtained after calcination at more than 5 hours for 500°C and temperature higher than 600°C for an hour but the single phase CCTO is not completely formed in both parameters for calcination process. After sintering, sample fired at 600℃ has been proved enough to induce single phase CCTO formed. Surface morphology has been evaluated by using SEM. The results shown as the calcination time and temperature increased, the amount and particle size of CCTO particles increased, the diffusion process had more time duration and also high temperature to generate energy for grain growth and hence the grain boundaries and porosity can be reduced. Dielectric properties measurement was done by using Impedance Analyser in 1 MHz – 1 GHz and Network Analyser in 1GHz – 10 GHz. The overall dielectric results have shown that, the dielectric constant and dielectric loss increase with an increase of microwave irradiation time during calcination. On the other hand, the dielectric constant and dielectric loss decrease with an increase of calcination temperature. By comparing the results between calcination time and temperature, it showed low temperature and longer time more effective than higher temperature but shorter time.