Effects of MgO coating on microstructure and dielectric properties of BaTiO3

MgO-doped barium titanate, containing 0.5-3.0 mol% MgO, was prepared by ball milling BaTiO3 and MgO, followed by drying. MgO-coated barium titanate of the same composition was prepared by homogeneous precipitation in aqueous solution using magnesium chloride and urea, followed by drying and calcination at 700 C, forming a core-shell structure. Uniaxially pressed specimens were sintered at 1320 C and characterised by microstructural studies, XRD, and measurement of the dielectric constant over the temperature range -55 to 150 C. The dielectric properties of the mixed and coated materials were different, attributed to the differences in microstructure and distribution of MgO. The high level of MgO dopant in the shell structure lowered the Curie temperature. It was concluded that coating enhanced the distribution of MgO in the BaTiO3 matrix, giving a homogeneous microstructure. 25 refs.