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Deng X.,Chongqing University | Deng X.,Chongqing University of Science and Technology | Deng X.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Huang J.,Chongqing University | And 8 more authors.
Journal of Alloys and Compounds | Year: 2016

Pure-phase perovskite BiFeO3 thin films were successfully deposited on the Pt substrates via radio frequency magnetron sputtering. The effect of O2/Ar ratio on the microstructure of BFO thin film was firstly investigated. The result shows that when O2/Ar ratio is 1:10, the BFO thin film exhibits a single perovskite phase with a dense structure. The effect of annealing temperature on the microstructure, ferroelectric, dielectric and magnetic properties of obtained thin film was subsequently investigated. The XRD result indicates that impurity phases appear whenever the annealing temperature is increased or decreased. Compared with other annealing temperatures, the BFO thin film annealed at 600 °C exhibits higher remnant polarization 2Pr of 23.26 μC/cm2, relatively larger coercive electric filed 2Ec of 563 kV/cm, higher dielectric constant of 150, lower dielectric loss of 0.03, lower leakage current density of 3.6 × 10-4 A/cm2, and saturation magnetization of 0.0036 emu/cm3. Our results provide useful information with preparing single and pure BFO thin films prepared by radio frequency magnetron sputtering to some extent. © 2016 Elsevier B.V. Source


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2014

Barium zirconate titanate ceramics were fabricated by microwave sintering. Effects of microwave sintering time on microstructure, dielectric and ferroelectric properties of barium zirconate titanate ceramics have been investigated. The result shows that the ceramic samples sintered at 2.5 kW for 15–30 min are single phase perovskite structure and there is no secondary phase observed. As the microwave sintering time extends, barium zirconate titanate ceramics become more uniform and the grain size increases. The data of dielectric properties indicate that the samples prepared by microwave sintering for 15–30 min are the ferroelectrics with diffuse phase transition and the diffuseness of phase transition weakens with the extending of microwave sintering time. As microwave sintering time increases, the remnant polarization increases initially and then decreases. Moreover, the remnant polarization and the coercive field of the samples sintered for 15 and 20 min decrease as measuring frequency increases, but the measuring frequency has little effect on ferroelectricity of the sample sintered for 30 min. The temperature dependences of hysteresis loops further prove that the samples are ferroelectrics with diffuse phase transition. © 2014, Springer Science+Business Media New York. Source


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.,Chongqing University of Science and Technology | Fu C.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Journal of Alloys and Compounds | Year: 2014

Ti-doped bismuth ferrite thin films were prepared via sol-gel spin-coating method. The effects of titanium on the microstructure, optical, leakage, ferroelectric and photovoltaic characteristics have been investigated systematically. The result shows that bismuth ferrite thin films doped with 0-8 at.% Ti are rhombohedral distortion perovskite structure. The addition of titanium inhibits the grain growth and enhances the thickness uniformity and can decrease the band gap of bismuth ferrite thin films. The leakage current of bismuth ferrite thin films is effectively reduced by adding a certain amount of titanium and the leakage mechanism has been investigated. Addition of titanium increases the remnant polarization of the films. As titanium content increases, the short circuit photocurrent density decrease first and then increase, while the open circuit photovoltage increase first and then decrease. The power conversion efficiency of Ti-doped bismuth ferrite thin films increases as titanium content increases, which can be explained as a result of the increased remnant polarization and decreased band gap. © 2014 Elsevier B.V. All rights reserved. Source


Cai W.,Chongqing University of Science and Technology | Cai W.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Fu C.L.,Chongqing University of Science and Technology | Fu C.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 7 more authors.
Materials Science Forum | Year: 2015

Bismuth ferrite is an important material in ferroelectric photovoltaic field, because of its narrow band gap and large polarization. Doping is a common method to further improve the photovoltaic properties of bismuth ferrite. Mn-doped bismuth ferrite thin films were prepared by sol-gel method. The effects of manganese on the crystal structure, ferroelectric and photovoltaic properties have been investigated. The result indicates that Mn-doped bismuth ferrite thin films are single phase and the lattice constant increases with the increase of manganese content. As manganese content increases, the remnant polarization and coercive electric field increase, while the short circuit photocurrent density and power conversion efficiency decrease. The open circuit photovoltage increases first and reaches the maximum and then decreases as manganese content increases. The results indicate that enhanced ferroelectricity caused by addition of manganese doesn’t make improvement on the photovoltaic characteristic. © (2015) Trans Tech Publications, Switzerland. Source


Luo X.D.,Chongqing University of Science and Technology | Luo X.D.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | Gao R.L.,Chongqing University of Science and Technology | Gao R.L.,Chongqing Key Laboratory of Nano Micro Composite Materials and Devices | And 10 more authors.
Physica B: Condensed Matter | Year: 2016

Effects of oxygen vacancies on the electrical transport properties of oxygen stoichiometric La0.8Sr0.2MnO3 and oxygen-deficient La0.8Sr0.2MnO3-δ films have been investigated. The result presents that the oxygen-deficient films annealed in vacuum show obvious increase of resistance and lattice parameter. With the sweeping voltage or temperature increasing, the resistance exhibits obvious bipolar switching effect, no forming process was needed. Oxygen deficiency in the annealed film leads to the formation of a structural disorder in the Mn-O-Mn conduction channel due to the accumulation of oxygen vacancies under high external electric field or temperatures and hence is believed to be responsible for the bipolar resistance switching effect and the enhanced resistivity compared with oxygen stoichiometric La0.8Sr0.2MnO3 film. These results may be important for practical applications in photoelectric or storage devices and point to a useful direction for other oxidizing materials. © 2015 Elsevier B.V. All rights reserved. Source

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