Structure–properties correlation in (1 − x)Bi0.90Pr0.10FeO3–(x)Ca0.5Sr0.5TiO3: phase evolution, optical, and electrical properties

Abstract

Recently, the search for novel multiferroic materials with enhanced multifunctional properties has become a major focus of the research community. However, achieving the desired multiferroic performance in single-phase BiFeO₃ ceramics remains a significant challenge. In the present study, solid solutions of (1 − x)Bi_0.90Pr_0.10FeO₃–(x)Ca_0.5Sr_0.5TiO₃ with x = 0.00, 0.05, 0.10, and 0.15, denoted as BPFO–CSTO, were synthesized via a conventional solid-state reaction route. X-ray diffraction patterns, analyzed by Rietveld refinement, revealed a coexistence of rhombohedral (R3c) and orthorhombic (Pnma) phases in all compositions, with the orthorhombic fraction increasing at higher CSTO concentrations. The Fe–O–Fe bond angle increased with increasing x (i.e., from 153.1° for x = 0.0 to 162.7° for x = 0.15), which plays a critical role in determining both magnetic and optical properties. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy was used to examine the grain morphology, grain boundaries, and compositional homogeneity of fractured sintered pellets. Room-temperature dielectric properties measurements demonstrated the significant influence of CSTO incorporation on the dielectric behavior of BPFO ceramics. Electrical conductivity analysis reveals conductions mechanism: holes and electrons hopping near room temperature, small polarons at intermediate temperatures, and ionic conduction via oxygen vacancies at higher temperatures. Modified Curie–Weiss and Vogel–Fulcher fits revealed that relaxor behavior increased with increasing CSTO percentage. Furthermore, UV-visible spectroscopy revealed a reduction in the optical bandgap from 2.21 eV (x = 0.0) to 2.13 eV (x = 0.15), positioning these materials within the visible spectrum and suggesting their suitability for photovoltaic applications.