Anjali Varshney, Sunil K. Chauhan, Manoj Kumar, O. Raymond Herrera, Subhash Sharma
High Resolution Image Download MS PowerPoint Slide The structural, electronic, and multifunctional properties of undoped and Ho/Ca codoped BiFeO 3 (BFO) nanoparticles were studied through aliovalent A-site substitution. Rietveld refinement confirmed phase-pure rhombohedral BFO at 600 °C, while Ho/Ca incorporation induced lattice contraction, compressive strain, and a rhombohedral to orthorhombic transition ( R 3 c → Pnma ). Co-doping of Ho/Ca reduced the particle size from 75 to 27 nm, introduced structural disorders, and increased the surface area, as verified by Electron microscopy, Raman spectroscopy, and BET. XPS analysis explicitly confirmed Ho 3 + /Ca 2 + substitution, revealed Fe 2 + /Fe 3 + coexistence, and also demonstrated a marked rise in oxygen vacancies. VBS and UV-visible analysis showed Fermi-level shifts and bandgap narrowing from 2.22 to 2.05 eV, which improved charge transport and visible-light absorption. Magnetic measurements revealed a nearly 6-fold enhancement in weak ferromagnetism from 0.109 to 0.609 emu g –1, originating from reduced size, lattice strain, and vacancy-driven Dzyaloshinskii–Moriya interactions, while ESR spectra confirmed suppression of the cycloidal spin structure and maximized spin canting in sample Bi 1–2 x Ho x Ca x FeO 3 at x = 0.05. Optical absorption evidenced defect-mediated transitions, and ferroelectric and leakage analyses identified Bi 1–2 x Ho x Ca x FeO 3 at x = 0.05 as the optimal composition balancing polarization retention with leakage suppression. Photocatalytic degradation of RhB followed, with Bi 1–2 x Ho x Ca x FeO 3 at x = 0.05 sample achieving a high-rate constant of 0.02501 min –1 and 97% degradation efficiency in 90 min, outperforming many oxide-based photocatalysts. Radical-trapping experiments identified ·OH as the primary active species driving the reaction. Overall, Ho/Ca codoping in BFO provides a powerful pathway to engineer crystal symmetry, defect chemistry, and spin interactions in BFO, delivering simultaneous improvements in their properties like ferroelectric, magnetic, and photocatalytic performance. This article revealed A-site aliovalent substitution in BFO as a versatile strategy for designing next-generation multifunctional perovskite materials.