Effect of Gd doping on the structure, dielectric and multiferroic properties of 0.7BiFe0.95Ga0.05O3-0.3BaTiO3 ceramics

The 0.7Bi(1-x)Gd(x)Fe(0.95)Ga(0.05)O(3)-0.3BaTiO(3) (BG(x)FG-BT, x = 0, 0.05, 0.1, 0.15, 0.2) ceramics were successfully synthesized via the conventional solid-state reaction method. The effects of Gd doping on crystal structure, microstructure, dielectric, ferroelectric and magnetic properties were systematically investigated. X-ray diffraction analysis indicates that Gd doping induce a structural transition from rhombohedral (R3c) to pseudocubic (P4mm) in BG(x)FG-BT ceramics. Scanning electron microscopy results show a decrease of grain size with doping Gd in BFG-BT. The average grain sizes of the ceramics range from 3.2 mu m to 6.2 mu m. The dielectric constant and loss tangent are drastically increased and reduced respectively with introducing Gd into the ceramics. Temperature dependent dielectric constant presents a broad peak in the vicinity of Neel temperature (T-N) for all the samples, signifying strong magnetoelectric coupling. An increment in T-N is also observed as a result of Gd-doping in the temperature regions of 230 to 340 degrees C. The leakage current density is reduced by about two orders of magnitude under the electric field of 20 kV/cm. This can be ascribed to the reduction of the oxygen vacancy concentration, which is confirmed by the X-ray photoelectron spectroscopy result. The ferroelectricity and ferromagnetism are also improved after the addition of Gd seen from the polarization hysteresis (P-E) loops and the magnetization hysteresis (M-H) loops. The greatly enhanced magnetism with M-r = 0.0186 emu/g and M-s = 1.084 emu/g is obtained in the ceramic with x = 0.2, almost three point six times larger than that of the undoped ceramic.