Yao Lu; Xiangxiao Meng; Zhipeng Pei; Kai Leng; Weiren Xia; Xinhua Zhu
Abstract
Double perovskite Ba2FeNbO6 (BFN) powders were synthesized by molten salt method. Their optical properties were characterized by UV-Vis absorption spectra, and the band gaps (Eg) were determined to be 2.12 - 2.25 eV. The Eg values were tuned by adjusting the processing parameters ...
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Double perovskite Ba2FeNbO6 (BFN) powders were synthesized by molten salt method. Their optical properties were characterized by UV-Vis absorption spectra, and the band gaps (Eg) were determined to be 2.12 - 2.25 eV. The Eg values were tuned by adjusting the processing parameters of molten-salt route (e.g., annealing temperature, holding time as well as the molten salt ratios). The varied Eg values are ascribed to the different content ratios of Fe 3+ to Fe 2+ ions and the oxygen vacancies in the BFN powders. Oxygen vacancies in the BFN powders result in the distortions of FeO6 octahedrons, leading to different Fe-O bond lengths. Thus, the overlapping between the O-2p < /em> and Fe-3d orbitals is changed, making the Eg values changed. A small absorption shoulder with absorption edge at 650 nm (Eg ~ 1.91 eV) observed in the BFN powders, was ascribed to the d-d electronic transition from the Fe 3d-b2g to Fe 3d-b1g orbitals, which were formed by further splitting of Fe 3d orbitals in the distorted octahedral field. The present work offers an effective approach to tuning the Eg of BFN powders, which find promising applications in the fields of photovoltaic and photocatalytic devices.
Pravin M. Tirmali; Sagar M. Mane; Snehal L. Kadam; Shrinivas B. Kulkarni
Abstract
The double perovskite materials show the magnetic semiconductor, magneto-optic and magneto-capacitance like interesting properties. It is predicted that the B-site substitution in this system may results in interesting properties. La2Ni1-xFexMnO6 thin films are deposited on Pt/Ti/ Si(100) substrate ...
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The double perovskite materials show the magnetic semiconductor, magneto-optic and magneto-capacitance like interesting properties. It is predicted that the B-site substitution in this system may results in interesting properties. La2Ni1-xFexMnO6 thin films are deposited on Pt/Ti/ Si(100) substrate by Pulse Laser Deposition (PLD) technique. The films were uniform, fine grain and stoichiometric deposited at very low O2 pressure. The XRD of La2Ni1-xFexMnO6 thin films exhibits rhombohedral (R-3) phase. The peak broadening appears in Raman spectra at antistretching (518 cm -1 ) and stretching (656 cm -1 ) modes with presence of overtone modes at 1308 cm -1 in La2Ni1-xFexMnO6 thin film samples. XPS analysis reveals the presence of La 3+ , NiO, Ni 3+ , Fe 3+ , Mn 3+ and oxygen vacancies in samples. The Ni 3+ and Mn 3+ antiferromagnetic coupling is responsible for decrease in saturation magnetization Ms from 4.78 to 2.74 µB/f.u as Fe substitution increases from 0.1 to 0.3 at 5K. The increase in grain size, peak broadening and decrease in magnetization of La2Ni1-xFexMnO6thin film samples suggest presence of antisite defects and antisite phase boundary. The present work will helpful to study the effect of B site substitution on La2NiMnO6 thin films structural, electronic and magnetic properties in order to make it suitable candidate for potential applications.
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