Effects of Ho3+ and transition metal ion doping on optical and magnetic properties of BiFeO3 nanopowders

BiFeO3 (BFO), Bi0.9Ho0.1FeO3 (BHFO), and transition metal (TM = Cr, Mn, Co, Ni, Cu, Zn) doped Bi0.9Ho0.1FeO3 (BHFO-TM) nanopowders were prepared by a double-solvent-based sol–gel route. The effects of Ho3+ and TM ion co-doping on the structural, morphological, optical, and magnetic properties of BFO nanopowders were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–Vis-NIR Spectrophotometer, and vibrating sample magnetometer. XRD patterns confirmed the distorted perovskite structure with R3c space group for all BHFO and BHFO-TM samples. TEM images identified that the particles of all BHFO and BHFO-TM samples were structured at the nanoscale (50 ~ 90 nm). BHFO-TM samples represented different visible light absorption and further decreased the band gap of BFO. The band gap of BHFO-Co nanoparticles (NPs) was the least (1.70 eV), which was a promising material for photocatalyst and photovoltaic devices. The magnetic tests indicated that BHFO-Cr in the BFO, BHFO, and BHFO-TM NPs samples had stronger ferromagnetic property with a small coercive magnetic field (H c  = 82 Oe), which is suitability for device applications. The mechanisms of the effects of Ho3+ and transition metal ion doping on optical and magnetic properties of BFO nanopowders were discussed in detail.