Influence of Ba and Mo co-doping on the structural, electrical, magnetic and optical properties of BiFeO₃ ceramics

In this work, ${Bi}_{0.8}{Ba}_{0.2}{Fe}_{1-x}{Mo}_x{O}_3$ (x = 0, 0.5, 0.10 and 0.15) ceramics were synthesized by conventional solid-state reaction to evaluate the influence of Ba²⁺ and Mo⁶⁺ co-doping on the structure, morphology, electrical, magnetic and optical properties of ${BiFeO}_3$ ceramic. Rietveld refinement of x-ray diffraction data was done to obtain the subtle structural information. A tetragonal structure of P4mm type was revealed for ${Bi}_{0.8}{Ba}_{0.2}{FeO}_3$ (x = 0) ceramic. Evolution of rhombohedral (R3c) phase was observed with Mo⁶⁺ doping and a complete transformation to R3c phase from P4mm was found for 15 wt% Mo⁶⁺ doping. This type of transformation causes distortion in the structure and results in changing bond angle. Magnetization was found to be improved with increasing the percentage of Mo⁶⁺ up to 10 wt%. Canting of spin due to the change in Fe-O-Fe bond angle is believed to be the main reason behind this improvement. One secondary phase ${BaMoO}_4$ was found and becomes prominent with Mo⁶⁺ doping. Possible formation of this impurity and its correlation with properties are explained. Microstructural analysis was done to observe the Ba²⁺ and Mo⁶⁺ co-doping effect on grain size and distribution. A correlation of grain size with electric and magnetic properties is drawn and elucidated. Dielectric constant shows an increasing trend with Mo⁶⁺ doping. Reduction in oxygen vacancy, due to charge compensation upon high charged Mo⁶⁺ addition, believed to be the staple reason behind the dielectric constant increment. Lastly, optical band gap energy found to be decreased with the addition of Mo⁶⁺ and possible reasons behind this are evaluated. Overall, co-doping of Ba²⁺ and Mo⁶⁺ found to have a positive influence over materials electrical, optical as well as magnetic property. (paper)