BaGeO3 as sintering additive for BaTiO3–MgFe2O4 composite ceramics

Abstract

BaTiO3–MgFe2O4 composites (30 wt% MgFe2O4) with a small addition of BaGeO3 as a sintering additive were synthesized by a one-pot Pechini-like sol–gel process. Nano-crystalline composite powders with a crystallite size of about 10 nm were obtained after reaction at 700 C for 1 h. Magnetic investigations suggest that the nano-powder is in its superparamagnetic state at room temperature. The addition of BaGeO3 leads to an improved sintering behaviour. DTA measurements reveal the formation of a liquid phase at 1164(3) C. Dense ceramic bodies (relative density $ 90%) were obtained after sintering for 1 h at 1150 C. SEM investigations prove a 0–3 connectivity and show that the addition of BaGeO3 promotes the grain growth leading to particles up to 4 mm. In contrast, fine-grained composite ceramics with smaller particles up to 230 nm were obtained after a two-step sintering process. Magnetic measurements indicate a ferrimagnetic behaviour with coercivity values up to 70 Oe depending on the sintering procedure. Furthermore, addition of BaGeO3 results in an increase of the relative permittivity, whereas the dissipation factor slightly decreases.