Study on quantitative Rietveld analysis of XRD patterns of different sizes of bismuth ferrite.

Bismuth ferrite (BiFeO3 or BFO), is an extremely promising multiferroic material having broad range of applications. In the present study, we investigated the optimization of annealing temperature for the preparation of pure phase bismuth ferrite using quantitative Rietveld analysis of XRD patterns. The rhombohedral structure was confirmed by X-ray diffraction with R3c space group as a primary phase (pure BFO) along with a cubic secondary phase (Bi25FeO40) having space group I23. The quantitative analysis of refine data shows the decrease in the values of fitting parameters in case of double refinement and hence convergence towards the best fitting. Also, with the increase in annealing temperature, very nominal decrease in phase percentage of secondary phase was observed. At annealing temperature of 780 °C, the intensity of (110) planes suddenly becomes more in comparison to (104) planes. The average crystallite size of samples was calculated using Scherrer formula, W–H plot method, and Rietveld method, and lattice strain was derived from the W–H plot method. Overall, the crystallite size increases with the increase in annealing temperature. It has been also observed that the strain, lattice parameters, unit cell volume, and effective bond lengths decrease with the increase in annealing temperature, but no significant change was observed in bond angles with the variation in annealing temperature. [ABSTRACT FROM AUTHOR]