Effect of donor and acceptor dopants on the microstructure and dielectric properties of barium titanate based ceramics

Abstract

This paper examined the microstructural and dielectric characteristics of BaTiO3 - based ceramics of the general formula BaTi1-x-yNbxMnyO3. The concentration of Mn as acceptor was variable 0.01 and 0.05 at%, while the donor (Nb) was fixed at 0.5 at%. The starting ceramic powders were produced by a conventional solid-state reaction method and sintered at 1290 and 1320oC. In BaTiO3 ceramics doped with a higher Mn concentration (0.05 at% Mn) at a sintering temperature of 1290?C, a bimodal structure with a grain of 10-30 ?m, and 1-5 ?m, was obtained. Sintering at a higher temperature (Tsin = 1320?C), regardless of Mn content, provides the achievement of a uniform microstructure with grains under than 6 ?m. The ceramics doped with 0.01 at% Mn and sintered at 1320?C are characterized by high values of the dielectric constant at room temperature and notable changes in the dielectric constant with temperature. Nb-0.05Mn BaTiO3 doped ceramics sintered at 1290?C show lower dielectric constant values due to the presence of Mn-enriched areas representing paraelectric regions. Areas richer in Mn are associated with the fine-grained structure. The dielectric constant in the investigated systems achieves a constant value for frequencies higher than 3kHz. The Curie temperature of all samples was shifted to lower values in relation to undoped BaTiO3 ceramics. According to Curie-Weiss law were determined the Curie constant C and the Curie temperature Tc.