Tungsten Trioxide Electric Transport Ⅰ

In the diamond resistivity, we explore resistivity, grain resistance, grain boundary resistance and other physical relaxation frequency variation by measuring the DC resistivity method and AC impedance spectra at high pressure and in the pressure range 36GPa. Taking WO3 ceramics in electrical transport properties of under high pressure as experiment, we  found that discontinuous change in the resistivity of the sample which appears in pressure at 1.8, 21.2 and 30.4GPa, which reflects the pressure-induced structural phase transition WO3. After relieving the resistivity and it did not recover to its original value, which indicating that the structure of WO3 phase transition is irreversible.

 
Four-electrode preparation process schematic diagram

In addition, the grain resistance and abnormal changes in the activation energy of conduction 3 and 10GPa is different from previous research by Raman and other structural phase transition related.  The law is that under high pressure resistivity with temperature variation shows WO3 from atmospheric pressure to nature 25.3GPa consistent with semiconductors. The new peaks by synchrotron radiation X-ray diffraction experiments at about 24 and 31GPa emergence confirms the structural phase transition, indicating the correctness of the results of electrical measurements and related analyzes.

We found  that the resistivity of the sample appeared discontinuous changes in the 4.3 and 10.5GPa by measurement of nanometer WO3 high-pressure in-situ resistivity, which reflects the electronic structure of nanometer WO3 phase transformation, the scale effect of grain led to a phase change of the hysteresis ; changes in the slope of the resistivity at 24.8 and 31.6GPa reflect the structural phase transition of nanometer WO3; resistivity from 36GPa relief to atmospheric pressure and did not return to the initial state value, all that indicates a structural phase transition of nanometer WO3 is irreversible phase variable. Variable temperature resistivity studies shows that nanometer WO3 from atmospheric to 36GPa keeping the transmission characteristics of the semiconductor, which is similar to the material WO3. The discovery of frequency AC impedance spectra appears under pressure grain boundary effects; grain resistance at 4.6 and discontinuities 10.3GPa department also provides the basis for the electronic phase transition; pressure-induced relaxation frequency changes show 10.3GPa relaxation time in the electronic phase transition at the shorter. Traces of grain boundary relaxation frequency also shows grain boundary effects are not completely disappeared, which is consistent conclusions with Nyquist impedance spectra.
 

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