We have investigated the structure, optical and magnetic properties of ferroelectric KNb1-xFe2O3-δ （x=0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25） synthesized by a traditional solid-state reaction method. According...We have investigated the structure, optical and magnetic properties of ferroelectric KNb1-xFe2O3-δ （x=0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25） synthesized by a traditional solid-state reaction method. According to the X-ray diffraction and the results of Rietveld refinement, all the samples maintain orthorhombic distorted perovskite structures with Amm2 space group without any secondary phase, suggesting the well incorporation of Fe ions into the KNbO3 matrix. With the increase of Fe concentration, the band gap of each sample is decreased gradually, which is much smaller than the 3.18 eV band gap of pure KNbO3. Through X-ray photoelectron spectrum analysis, the increased density of oxygen vacancy and Fe ions may be responsible for the observed decrease in band gap. Compared with the pure KNbO3, Fe doped samples exhibit room-temperature weak ferromagnetism. The ferromagnetism in KNb1-xFexO3-δ with low-concentration dopants （x=0.01-0.10） can be attributed to the bound magnetic polaron mediated exchange. The enhancement of magnetism for the high-concentration （x=0.10-0.20） doped samples may arise from the further increase of magnetic Fe ions.展开更多
基金The work was supported by the Fundamental Research Funds for the Central Universities, SCUT （No.2014ZZ0069） and the National Natural Science Foundation of China （No.21473211 and No.11304098）.
文摘We have investigated the structure, optical and magnetic properties of ferroelectric KNb1-xFe2O3-δ （x=0, 0.01, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25） synthesized by a traditional solid-state reaction method. According to the X-ray diffraction and the results of Rietveld refinement, all the samples maintain orthorhombic distorted perovskite structures with Amm2 space group without any secondary phase, suggesting the well incorporation of Fe ions into the KNbO3 matrix. With the increase of Fe concentration, the band gap of each sample is decreased gradually, which is much smaller than the 3.18 eV band gap of pure KNbO3. Through X-ray photoelectron spectrum analysis, the increased density of oxygen vacancy and Fe ions may be responsible for the observed decrease in band gap. Compared with the pure KNbO3, Fe doped samples exhibit room-temperature weak ferromagnetism. The ferromagnetism in KNb1-xFexO3-δ with low-concentration dopants （x=0.01-0.10） can be attributed to the bound magnetic polaron mediated exchange. The enhancement of magnetism for the high-concentration （x=0.10-0.20） doped samples may arise from the further increase of magnetic Fe ions.
