Calcium Titanate Ceramics Obtained by Combustion Synthesis and Two-Step Sintering
Calcium titanate powder was successfully prepared from duck eggshell and anatase titanium dioxide with a magnesium inductant via combustion synthesis in argon. As-combusted products were leached with diluted HCl. In XRD analysis, as-leached powders exhibited a major phase of CaTiO3 with a perovskite structure. The particle size, observed by SEM, was approximately 240 nm. As-leached powders were densified by single-step (SST) and two-step sintering (TSS) to produce calcium titanate ceramics. The first step of all TSS conditions was fixed at 1350 oC and holding times (t1) at this temperature were varied up to 120 min. Calcium titanate ceramic obtained from holding for 120 min had a grain size of 2.18 m, relative density of 86.68 % and a dielectric constant of 92. Two-step sintered ceramic had the highest density (95.73 %) and best dielectric properties (dielectric constant = 110, dielectric loss = 0.02) when the holding temperature (T2) was 1250 oC. Calcium titanate ceramics processed by two-step sintering had denser microstructures and higher dielectric constants than single-step sintered ceramic due to grain boundary diffusion and the simplicity of relaxation polarization.
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