Papers by Author: Qun Wang

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Authors: Rui Dong, Qun Wang, Li Dong Chen, Xiao Min Li
Abstract: A simple chemical solution deposition method was developed for the preparation of La0.7Ca0.3MnO3 (LCMO) thin films. The LCMO thin films were prepared on Si/SiO2/TiO2/Pt substrates by spin-coating method, followed by heat-treatment at 900°C. The fabrication process of the LCMO thin film was investigated by means of TG-DSC, FTIR, XRD, FE-SEM and EPMA. The electric pulse induced reversible resistance switching is observed in the Ag-LCMO-Pt sandwich structure.
Authors: Jun Jiang, Li Dong Chen, Sheng Qiang Bai, Qin Yao, Qun Wang
Abstract: The n-type Bi2(Te,Se)3 thermoelectric materials doped with different contents of TeI4 were fabricated through the spark plasma sintering (SPS) technique at 693K under a pressure of 60MPa. The sintered materials were rather dense and showed preferred grain orientation. Electrical conductivity (s), Seebeck coefficient (a), and thermal conductivity (k) were measured in the temperature range of 300-500K. The optimal figure of merit ZT (ZT=a2sT/k) of the sintered material in the direction perpendicular to the pressing direction showed a value of 0.75 for the sample containing 0.14wt% TeI4.
Authors: Qun Wang, Rui Dong, Li Dong Chen, Tong Lai Chen, Xiao Min Li
Abstract: A novel electric-pulse-induced reversible resistance (EPIR) change effect was observed in Ag/Ln1-xCaxMnO3/Pt (Ln= Pr, La) sandwich structure at room temperature without applied magnetic field. The Ln1-xCaxMnO3 films were grown on Pt/Ti/SiO2/Si substrate. The resistance of the Ag/Ln1-xCaxMnO3/Pt sandwich structure increases and reaches at a saturated high resistance state after applying a certain number of electric-pulse from Pt bottom electrode to Ln1-xCaxMnO3 layer, while it decreases and switches to a saturated low resistance state when the pulse polarity reversed. It is also found that the EPIR effect in the /Ln0.7Ca0.3MnO3/Pt system exhibits “fatigue” behavior, that is, for the high resistance state activated by electric-pulse, along the time after pulsing, the resistance decreases slowly after a certain stable stage; otherwise, the resistance change ratio decreases as the number of the high-low resistance switching circle increases. For the fatigue phenomenon with time, a resistance change with three stages was observed and a simple mechanism of the EPIR was proposed.
Authors: Chun Fen Wang, Qun Wang, Sheng Cong Liufu, Qin Yao, Li Dong Chen
Abstract: High dense Bi2Te3 nanowire arrays were fabricated in porous anodic alumina (PAA) by electrochemical deposition. A macro-integration measurement was used to study the thermoelectric properties of a superimposed layer of Bi2Te3/PAA structure. In this macro-integration system, meaningful amounts of heat will transport along Bi2Te3 nanowire arrays, and so the measurement errors of micro-current and micro-temperature difference of individual nanowire can be eliminated. The influences of wire diameter, area fraction of wires and interface thermal resistance in the sandwich structure on the measurement accuracy of Seebeck coefficient and electrical conductivity of Bi2Te3/Al2O3 system were discussed. The experimental electrical conductivity is close to the theoretically calculated value. Further improvement in eliminating the interface thermal resistance would bring more reliable result in Seebeck coefficient measurement. The macro-integration measurement is a practical method to evaluate the thermoelectric properties of thermoelectric nanowire arrays.
Authors: Qun Wang, Dong Sheng Yang, Cheng Jun Duan, Rui Li, Mei Ling Zhou
Authors: Wei Dong Yu, Xiao Min Li, Yi Wen Zhang, Rui Yang, Qun Wang, Li Dong Chen
Abstract: A noncrystalline SrTiO3 (STO) thin film was grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The Pt thin film was deposited on STO film as top electrode, forming a symmetric structure (Pt/STO/Pt) to exclude the influence of the electrical difference in STO-electrode interfaces. It was found that a stable bipolar resistive switching was obtained in this structure. In a current sweep, an obvious S type negative differential conductance (NDC) phenomenon was found in both polarities. And in a voltage sweep, no NDC was observed due to the current control mechanism of S type NDC effect. The possible mechanism of this effect is discussed preliminarily.
Authors: Qun Wang, Jian Lin Shi, Li Dong Chen, Dong Shen Yan
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