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 1350C 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?C. 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.
Calcium titanate ceramics obtained by combustion synthesis and two-step sintering