Effects of Bi2O3 and MgO on microstructure and dielectric properties of BaTiO3–(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 system

Abstract

Bi2O3- and MgO-doped BaTiO3–(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 (BT–NBMT) ceramics were synthesized from a solid-state approach, and then the impacts of Bi2O3 and MgO dosages on the structures and dielectric characteristics were studied. Obvious dual peaks were observed with Bi2O3 dosage to 0.04 and MgO dosage to 0.02. The low-temperature dielectric stability and grain size of the Bi2O3 dopant were improved, while those of the MgO dopant hardly changed with MgO dosage to 0.02, indicating the core/shell microstructure of BT–NBMT was formed following the dissolving-precipitating mechanism of BT systems doped with low-melting-point substances. The low-temperature dielectric stability of the Bi2O3- or MgO-doped BT–NBMT ceramics first improved and then deteriorated with the increase of doping concentrations. High-temperature stability and diffuse-state transition were found in the optimal ceramics. The second phases of Bi2O3 and MgO, magnesium titanium compounds were observed in Bi2O3 and MgO dopants, respectively. Bi2O3-doped and MgO-doped ceramics exhibited a fine-grained microstructure and significant grain growth, respectively, and the core/shell microstructure was responsible for the dielectric temperature stability for Bi2O3 dopants and collapsed to a homogeneous one with remarkable grain growth and the second phases for MgO dopants.