Xisong Zhou

Tsinghua University, Beijing, Beijing Shi, China

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Publications (9)12.08 Total impact

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    ABSTRACT: The Li-doped Ni–Si–O thin films ( Li <sub>x</sub> Ni <sub>0.90-x</sub> Si <sub>0.10</sub> O , x=0.0–0.05 ) have been prepared by a sol-gel spin-coating method on silicon and quartz glass substrates. Analysis of phase composition and microstructure indicates that the films consist of cubic NiO phase and amorphous phase as annealed at 700 ° C for 5 min . With the Li-doping concentration increasing, the core-level photoemission spectra show that a loss of the double-peak structure of the Ni 2p<sub>3/2</sub> main line can be observed and current density of the films increases greatly, which should be ascribed to the increase of the hole carriers induced by the Li doping. Ultraviolet-visible absorption spectra indicate that the absorption edge of the films exhibits a redshift due to the related defects.
    Journal of Applied Physics 09/2006; · 2.21 Impact Factor
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    ABSTRACT: M2MgSi2O7:Eu, Dy (M: Ca, Sr, Ba) phosphors were prepared via sintering at 1300 °C for 3 h in a weak reductive atmosphere of flowing 5% H2–95% N2 gas. The emission spectra of these phosphors showed that the main emissions are peaking at 537.5, 475.6 and 500.3 nm due to 4f → 5d transitions of Eu2+. The decay curves indicated that all of these phosphors have long afterglow feature, especially Sr2MgSi2O7:Eu, Dy phosphor. It is the Dy3+ trap levels that resulted in the long afterglow in M2MgSi2O7 hosts.
    Materials Chemistry and Physics 01/2003; · 2.07 Impact Factor
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    ABSTRACT: Bulk samples of quasi-binary compounds in the Sn(Pb)Te-Bi2Te3 system were prepared by solvothermal method followed by a sintering procedure of compacted pellets. The formation mechanism of the precursor powders, microstructure and thermoelectric properties of the final bulk samples were studied.
    Science in China Series E Technological Sciences 01/2003; 46(5):509-514. · 1.02 Impact Factor
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    ABSTRACT: Eu3+-activated Y2O3 phosphor co-doped with Ti4+ or/and Mg2+ ions were prepared by calcinating the precursor powders in the 98%N2–2%H2 atmosphere. Red long afterglow was observed in the Y2O3:Eu3+, Ti4+, Mg2+ after excitation by 254 nm light, and the duration can reach nearly 1.5 h in the light perception of the dark-adapted human eyes (0.32 mcd/m2). The main emission peaks were ascribed to Eu3+ ions transition from 5DJ (J=0,1,2) to 7FJ (J=0,1,2,3,4), and the afterglow may be ascribed to some suitable complex trap centers produced by the introduction of Ti4+ and Mg2+ ions in the Y2O3 host lattice.
    Journal of Alloys and Compounds 01/2003; 361(1):92-95. · 2.73 Impact Factor
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    ABSTRACT: (Na0.5Bi0.5)(1−1.5x)EuxTiO3 ceramics have been prepared by solid state reaction at 1120°C for 2 h. Scanning electronic micrograph results indicate that the doped Eu2O3 can prohibit the grain growth. With increasing the doped amount of Eu2O3, the phase transformation (rhombohedral→cubic) can be observed in the X-ray diffraction patterns, and correlated with a strong decrease in the piezoelectric properties d33. The dielectric constants of poled and unpoled Na0.5Bi0.5TiO3 (NBT)-0 samples vary greatly as compared to NBT-5 sample due to the change of crystal structure.
    Materials Science and Engineering B 01/2003; 99(1):449-452. · 1.85 Impact Factor
  • Ce Wen Nan, Xisong Zhou, Jun Nan, Junbo Wu
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    ABSTRACT: In every electroceramic there exist variations throughout the microstructure of both grain size (and shape) and electrical properties of individual grain boundaries. To calculate the effects of such microstructural variations on the frequency-dependent impedance/dielectric behavior, we describe a generalized statistical effective-medium approach based on effective-medium theory. To illustrate the predictions of the approach, the effect of various distributions in the grain boundary conductivity and the grain size, as well as the grain shape and porosity, are considered. The calculations show that such variations lead to depression of the boundary arc and deviations of the impedance spectra from the well-known brick-layer model with an idealized microstructure consisting of identical grains and grain boundaries. © 2001 American Institute of Physics.
    Journal of Applied Physics 03/2001; 89(7):3955-3959. · 2.21 Impact Factor
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    ABSTRACT: Oxide ceramics have recently attracted much attention as candidate thermoelectric materials due to their special potential for applications in power generation using waste heat. In this paper, (Na<sub>x</sub>Ca <sub>1-x</sub>)<sub>3</sub>Co<sub>4</sub>O<sub>9+δ</sub> (x=0.05-0.2) polycrystalline samples with a layered structure were prepared by a sol-gel method followed by a low-temperature sintering procedure. The electrical conductivity, the power factor and thermal conductivity basically increase with increasing temperature. The figure of merit is smaller than that of traditional thermoelectric alloys, which is about 1.1×10<sup>-4</sup> K<sup>-1</sup> at 700°C in the sample (Na<sub>x</sub>Ca<sub>1-x</sub>)<sub>3</sub>Co<sub>4</sub>O <sub>9+δ</sub> (x=0.05-0.2)
    Thermoelectrics, 2001. Proceedings ICT 2001. XX International Conference on; 02/2001
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    ABSTRACT: Performance of thermoelectric materials and devices depends upon various features on different levels from microscopic to macroscopic scales. On the atomic scale, to find new multi-component compounds with complex electronic and crystal structures is a way to high-Z thermoelectric materials. On the nano-scale, quantum wells, wires and dots are considered to be the dawn for breaking the traditional barrier of ZT~1 existing for several decades. From the point of view of microstructure, inhomogeneities in thermoelectric materials, such as interfaces/grain-boundaries and inclusions, have significant influences on their thermoelectric properties. On the macroscopic scale, the thermoelectric device functions depend on thermoelectric materials used for building the device and device configuration (such as multistage or segmented devices). This review briefly presents the state-of-the-art and perspectives in the multiscale understanding of thermoelectric materials and devices
    Thermoelectrics, 2001. Proceedings ICT 2001. XX International Conference on; 02/2001
  • Xisong Zhou, Jun Nan, Junbo Wu, Ce Wen Nan
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    ABSTRACT: Bismuth telluride based alloys have been a class of important thermoelectric materials. In this paper, polycrystalline samples of ternary compounds in the SnTn-Bi<sub>2</sub>Te<sub>3</sub> system were prepared by a rapid quenching of the melt followed by a sintering procedure of compacted pellets. The microstructure and thermoelectric properties, including Seebeck coefficient, electrical and thermal conductivities, of the samples were measured. The influence of processing routes, and constituent concentration on the thermoelectric properties was studied and discussed
    Thermoelectrics, 2001. Proceedings ICT 2001. XX International Conference on; 02/2001