Structure And Properties Of La-Doped And Ho-Doped Bismuth Ferrite Powders

BiFeO3(BFO) is one of the few multiferroic materials with ferroelectric and antiferromagnetic order in room temperature and applied to many modern technologies, such as information storage, sensing and so on. A site doped with rare earth elements can enhance the BFO ferroelectric and ferromagnetic. In this paper, the preparation, structural changes and magnetic properties of La-doped and Ho-doped bismuth ferrite powders have been studied. The main results are as follows:1. Bi1-xLaxFeO3 (BLFO, x=0.00,0.05,0.10,0.15,0.20,0.25,0.30,0.35,0.40) nanopowders were prepared by sol-gel method and characterized by X-ray diffraction and Raman spectra. The results showed that the lattice constants and cell volume decreased with the La content x increasing, and the crystal structure transformed from the R3c rhombohedra to the Amn2 orthorhombic with the La content x increasing to 0.30.2. When the La content is no more than 30%, the substitution of La for Bi causes the lattice distortion of BLFO, suppresses the spinning structure of spatial modulation and increases magnetic properities. When the doping concentration increases to 30%, the spinning structure is destructed by structural phase transition, leading to significant increase of magnetic properties.3. Bi1-xHoxFeO3 (BHFO, x=0.00,0.10,0.20,0.30,0.40) powders were prepared by glycine-nitrate process successfully. X-ray diffraction showed that substitution of Ho for Bi prevents the impurity phase Bi24Fe2O39 forming. And the small ionic radius of Ho can lead the distortion of the lattice and decrease the cell volume. When the Ho content increases to 0.30, BHFO structure transforms from rhombohedral to orthorhombic. The 8 Raman peaks of BFO were observed in wave number range of 100-700cm-1 at room temperature. When x=0.30, the Raman spectra has a remarkable change indicating a structural phase transition.4. The magnetic susceptibilityχand the remanent magnetization Mr of Bi1-xHoxFeO3 (x=0.00-0.40) increase with the Ho content increasing, but the coercivity Hc decreases at the same time. When the Ho content increases to 0.30, the substitution of Ho for Bi causes the lattice structure to transform, destructs the spin structure and leads significant enhancement of magnetism.