, Volume 27, Issue 21, pp 5713-5719

Dielectric properties and microstructural behaviour of B-site calcium-doped barium titanate ceramics

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Dielectric properties and microstructural behaviour of Ba1−x Sr x Ti1−y Ca y O3−y ceramics, where strontium and calcium were doped on the barium and titanium sites, respectively, within the range 0⩽x⩽0.24 and 0⩽y⩽0.05, were investigated. Calcium addition decreased the tetragonality,c/a, increased the unit cell volume, and lowered the Curie temperature, which were all attributed to the occupancy of Ca2+ ions on titanium sites. When sintered at a low oxygen partial pressure of 10−9 MPa, a resistivity higher than 1011 ω cm was maintained for the formulations containing B-site calcium substitution more than 0.5 mol %. With increasing the amount of calcium addition, the Curie peak was depressed and completely broadened for the compositions with calcium addition more than 3 mol %, where the average grain size was smaller than 1 μm. Co-firing with nickel electrodes in a reducing atmosphere also depressed the Curie peak and inhibited the grain growth due to the diffusion of nickel into the dielectrics.