Microstructure and dielectric properties of Mg-doped barium strontium titanate ceramics

The dielectric properties of Ba0.8Sr0.2TiO3 ceramics doped with Mg from 0.5 to 10 mol % have been investigated systematically. Two effects of Mg doping on the dielectric properties of the Ba0.8Sr0.2TiO3 ceramics have been observed. At low Mg doping concentrations (<2 mol %), Mg mainly acts as an acceptor dopant to replace Ti in the B site of ABO(3) perovskite structure, leading to a shift of Curie point (T-C) to lower temperatures and a diffused phase transition. The permittivity and dielectric loss are suppressed gradually as the Mg content increases and the grain size decreases drastically. At higher Mg doping concentrations (greater than or equal to2 mol %), further suppression of permittivity and losses without further T-C shift are observed, which indicates a "composite" mixing effect. The grain size remains almost constant. The solubility limit of Mg in the Ba0.8Sr0.2TiO3 appears to be similar to2 mol %. (C) 2004 American Institute of Physics.