Mössbauer Spectroscopy and Magnetic Properties of Bi0.8Ca0.2-xSrxFeO3 Nanoparticles by Sol-Gel Method

Abstract

Doping at A/B-sites can effectively improve the physical properties of perovskite ferrites. In this study, the performance of Bi_0.8Ca_0.2-xSr_xFeO₃ was investigated using the sol-gel autocombustion method. The results show that with an increase in x value, the grain size first increases and then decreases. With an increase in the doping concentration, the reunion phenomenon reduces, but the smoothness and flatness of the samples are also destroyed. Moreover, with increasing Sr²⁺ concentration, particle growth is inhibited, resulting in smaller particle sizes. When the Sr²⁺ concentration increases to a certain value, the environment becomes advantageous for particle growth and therefore the particle size increases. For x=0.13, small particles are obtained. With increasing Sr²⁺ concentration, the spatial modulation of the spin structure is destroyed, the lattice distorts, and the magnetic force is freed. Mössbauer spectrum measurements shows that when the Ca²⁺ concentration is greater than the Sr²⁺ concentration, Sr²⁺ ions replace Ca²⁺ ions; as a result, A-A magnetic superexchange diminishes, leading to a decrease in the hyperfine field. Appropriate doping of BiFeO₃ can improve its coercivity and refine its grains and result in a larger magnetic force.