Influence of calcination temperature on the properties and photocatalytic efficiencies of BiFe0.9Cu0.1O3 nanoparticles

Abstract

Abstract BiFe₀.₉Cu₀.₁O₃ nanoparticles were synthesized via a simple solution combustion method, and the effect of calcination temperature (500–800 °C) on their properties and photocatalytic performance was systematically investigated. The nanoparticles were characterized using XRD, FTIR, FE-SEM, BET surface area analysis, XPS, UV-Vis diffuse reflectance, photoluminescence, and VSM. XRD analysis confirmed a primary rhombohedral BiFeO₃ phase alongside a secondary orthorhombic Bi₂Fe₄O₉ phase. The results revealed a complex interplay between calcination temperature and material properties: the crystallite size increased with temperature up to 700 °C, then decreased slightly. At the same time, the specific surface area was maximized at 500 °C. The optical band gap reached a minimum of 3.30 eV at 500 °C, then widened at higher temperatures. VSM measurements revealed ferromagnetic behavior at room temperature, with the saturation magnetization peaking at 600 °C due to the suppression of the spin spiral structure and the presence of oxygen vacancies. The photocatalytic activity for methylene blue (MB) degradation under visible light was maximized at 500 °C, achieving 72.75% degradation efficiency after 160 min. This optimal performance is attributed to the synergistic combination of the highest specific surface area, a favorable band gap, and a high concentration of defect sites that suppress charge carrier recombination. The optimal sample demonstrated good stability and reusability over five cycles. Scavenger tests indicated that the hydroxyl radicals (HO • ) were the primary reactive species. The results confirm that solution combustion is an effective route for producing Cu-doped BFO nanoparticles, with the calcination temperature being a critical parameter for optimizing their photocatalytic performance.