Negative Permittivity in (V2O5)100-xSex Alloys
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- 作者：Sandeep Kohli ; Christopher D. Rithner ; and Peter K. Dorhout
- 刊名：Chemistry of Materials
- 出版年：2002
- 出版时间：September 2002
- 年：2002
- 卷：14
- 期：9
- 页码：3786 - 3792
- 全文大小：159K
- 年卷期：v.14,no.9(September 2002)
- ISSN：1520-5002
文摘
(V2O5)100-xSex (x = 9, 17, 25, 30 wt %) alloys have been prepared by quenching the meltfrom 1000 to 273 K in ice water. The XRD data show the presence of crystalline V2O5, V6O13,VO2, and Se phases. High-resolution XPS spectra for a Se 3d peak show the presence ofSeO2 and elemental Se phases in the samples. The presence of a reversible endothermicpeak 
343 K in the differential scanning calorimetric (DSC) curve of quenched samples isindicative of the monoclinic to tetragonal transformation in VO2. A selenium melting peakat 495 K is also present in the DSC curve, for x 
17. Room-temperature dielectricmeasurements in the frequency range 1 Hz to 100 kHz show the presence of negativepermittivity in samples with x < 30. Permittivity Vs temperature and loss-factor Vstemperature measurements in the temperature range 273-373 K and at a fixed frequencyof 1 kHz were reversible with hysteresis across the monoclinic to tetragonal transformationof VO2. A sample with x = 30 exhibits a minimum temperature range of hysteresis andlarge change in the value of permittivity. The diffuse reflectivity values for the sampledecreases with the increased selenium content until x 
17. For x > 17, the reflectivity ofthe samples increases with increased selenium content. This is explained in terms of theincreased V2O5 component in the samples.
343 K in the differential scanning calorimetric (DSC) curve of quenched samples isindicative of the monoclinic to tetragonal transformation in VO2. A selenium melting peakat 495 K is also present in the DSC curve, for x 17. Room-temperature dielectricmeasurements in the frequency range 1 Hz to 100 kHz show the presence of negativepermittivity in samples with x < 30. Permittivity Vs temperature and loss-factor Vstemperature measurements in the temperature range 273-373 K and at a fixed frequencyof 1 kHz were reversible with hysteresis across the monoclinic to tetragonal transformationof VO2. A sample with x = 30 exhibits a minimum temperature range of hysteresis andlarge change in the value of permittivity. The diffuse reflectivity values for the sampledecreases with the increased selenium content until x 17. For x > 17, the reflectivity ofthe samples increases with increased selenium content. This is explained in terms of theincreased V2O5 component in the samples.