Preparation and properties of (1 − x)BiFeO3–xBaTiO3 multiferroic ceramics

Solid solutions of (1 − x)BiFeO3–xBaTiO3 (0 ≤ x ≤ 0.30) have been prepared by a two-step solid state reaction. By comparison with other reported methods, a higher electrical homogeneity of the ceramic bodies resulted in better dielectric properties, with a single-component impedance plot, small losses and permittivities below 240. The maximum magnetization is observed for x = 0.05, which might represent the proper range of compositions for multiferroism at room temperature. In order to better understand the composition-dependent magnetic properties in correlation with the expected Fe2+/Fe3+ ratio fluctuations in the solid solutions, a detailed X-ray Photoelectron Spectroscopy (XPS) analyses were performed on the surfaces and on the fractured sintered bodies.

Research highlights▶ One of the research highlights is given by the (1 − x)BiFeO3–xBaTiO3 solid solutions prepared by two-step sintering method which demonstrated an improvement of the dielectric characteristics, by comparison with literature data: a higher electrical homogeneity of the ceramic bodies resulted in better dielectric properties, with a single-component impedance plot, small losses and permittivities below 240. ▶ The properties of the as-sintered BiFeO3 ceramics were investigated. In the low-temperature range, a linear non-saturated dependence M(H) was observed. After this experiment, the same BiFeO3 ceramic sample was subjected to a thermomagnetic measurements under a FH/FC cycle in the temperature range of (300–1000) K under a magnetic field. The magnetization decreases with temperature, showing a small anomaly at the Neél temperature TN ∼ 643 K on heating. A small thermal hysteresis of ∼60 K at the Curie temperature was noticed. ▶ The magnetic properties of the (1 − x)BiFeO3–xBaTiO3 ceramics was investigated in the paper. A composition and temperature-dependent magnetic order was found. The origin of the observed magnetic properties is also discussed. The present investigations demonstrates that the magnetic data shown a typical antiferromagnetism in BiFeO3 ceramics which can be turned into a ferrimagnetism by a FH/FC sequence under H  = 10 kOe. The thermomagnetic data indicate that magnetic properties are strongly composition and history-dependent and also that field cooling causes field-induced weak ferromagnetism in all the compositions.