Andrea Kirsch, M. Mangir Murshed, Melanie J. Kirkham, Ashfia Huq, F. Jochen Litterst and Thorsten M. Gesing

The Journal of Physical Chemistry C (2018) 122 (49), 28280–28291

https://doi.org/10.1021/acs.jpcc.8b05740

We report on temperature-dependent structural and spectroscopic features of (Bi_1–xFe_x)FeO₃ perovskite for x = 0.15 and 0.25. Samples were synthesized by heating quantum crystalline precursors obtained by the polyol method. Crystal structures of each composition were obtained from in-house X-ray, synchrotron X-ray, and time-of-flight neutron powder diffraction data Rietveld refinements. Partial replacement of the Bi site by the Fe³⁺ cation significantly changes the crystal physicochemical properties, such as thermal expansion, polyhedral distortion, Debye temperature, and vibrational and magnetic properties. Whereas BiFeO₃ is multiferroic, both Bi_0.85Fe_0.15FeO₃ and Bi_0.75Fe_0.25FeO₃ are found to be superparamagnetic, as observed by temperature-dependent Mössbauer and SQUID measurements. Lattice thermal expansion was modeled using the Debye–Einstein-anharmonicity approach. Debye temperatures obtained from the mean-squared atomic displacement parameter and lattice thermal expansion are compared. Temperature dependence of selective Raman modes is also analyzed.