Effect of La Dopant in Modified Bismuth Ferrite Ceramics

Abstract

The La modified bismuth ferrite perovskite Bi0.6La0.4FeO3 (BLF) is prepared by cost-effective high solid-solution casting technique. Formation of composite is checked through X-ray diffraction and also notable that there is phase transition from rhombohedral (R3c) to orthorhombic (Pbnm). The average crystalline size (DSC) and mechanical lattice strain are 63.8 nm and 0.147% respectively as calculated by Williamson-Hall method. The frequency bands corresponding to Bi-O, LaO, and FeO stretching vibration confirm that La +3 ions completely incorporate the Bi +3 ions in the A-site of the single perovskite. The SEM micrograph suggests that the sample has distinct grains and well-defined grain boundaries and the average grain size (DSEM) is about 13.9 μm. The rate of agglomeration that acquire in the sample (DSEM/ DSC = 219) confirms the excellent connectivity of grains which stands possible reason for the high dielectric and conductivity. The impedance analysis provided the fact that bulk resistance (Rb) decreases from 6.662 x 10 5 Ω at 25 0 C to 1.000 x 10 -2 Ω at 350 0 C; suggesting NTCR behaviour of the material. The activation energy increases from 201 meV to 677meV with temperature supports a thermally activated conduction mechanism. The thermally activated relaxation process is controlled by the immobile charge carriers at lower temperature range while controlled by defects at higher temperatures which suggests the presence of hopping mechanism. The gap between the peak of and is becoming wide with temperature suggests a non-Debye type character. The semicircular arcs in both Nyquist plots and Cole-Cole plots are confirming the semiconductor nature.