Structural, dielectric and multiferroic properties of Er and La substituted BiFeO3 ceramics

Erbium (Er) and lanthanum (La) substituted BiFeO3 (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi0.9-xLa0.1ErxFeO3 (x = 0.5, 0.07 and 0.1) (BLEFOx=0.05,0.07,0.1) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835 degrees C, whereas it is shifted to 792 degrees C for BLEFOx=0.1. The Raman spectra of BLEFOx=0.05,0.07,0.1 samples showed the shift of Raman modes to higher wavenumbers and suppression of A(1) modes indicating decrease in ferroelectricity. The Raman spectra also indicated the structural transformation due to Er and La substitution in BFO. On subsequent erbium doping, the intrinsic dielectric constant is found to decrease from 68 (for pure BFO) to 52 for BLEFOx=0.05 to 43 for BLEFOx=0.07 but increased to 89 for BLEFOx=0.1 when compared to pure BFO. The increase in Er content resulted in the increase in spontaneous magnetization (0.1178 emu/gat 8T for BLEFOx=0.1) due to collapse of spin cycloid structure. Ferroelectric remnant polarization of BLEFOx=0.05 and BLEFOx=0.07 decreases when compared to pure BFO while small remnant polarization (close to paraelectric behaviour) is evident for BLEFOx=0.1.