The Electrical Transport Properties And Structural Behavior Of SnO₂under High Pressure

Tin oxide (SnO2) is a typical wide bandgap semiconductor and a kind of excellentconductive material. SnO2has the good permeability to visible light and the good gassensitivity, so it was widely used in transparent conductive electrode, gas sensor andso on. Because of the potential application value of SnO2in the field of photoelectricdevice, SnO2has become a hot research topic. In recent years, the research of theelectrical transport properties is scarce for SnO2especially under high pressure. Theelectrical properties of SnO2have a great influence on its application value. On thisaccount, we study the properties of SnO2under high pressure by the numbers.In this paper, both in-situ electrical transport properties measurement and thediamond anvil cells were employed to investigate the synchrotron radiation X-raydiffraction experiment, DC resistivity test, AC impedance spectum experiment ofSnO2under high pressure. Combined with the first principles calculation,systematically study the electrical and structural properties of SnO2under highpressure.The main study results are listed as follow:1. The structural properties of SnO2under high pressure have been studied by thesynchrotron radiation X-ray diffraction experiment, we observe that all the diffractionpeaks had right shift and the peak value also decreased with the increasing pressure.The new diffraction peaks were observed at13GPa and19.2GPa, indicating thephase transition. SnO2samples from rutile structure into CaCl2-type then to pyritestructure transformation.2. According to the pressure dependence of electrical resistivity of SnO2, weobserved the discontinuous changes of electrical resistivity at10.6GPa,13.6GPa and18.5GPa. We thought that the discontinuous changes of the electrical resistivityreflected the phase transition of SnO2samples from rutile structure into CaCl2-type and because of the sample chamber the non-hydrostatic pressure cause CaCl2-typetranslate into α-PbO2structure, and finally into pyrite structure at18.5GPa.3. By AC impedance spectroscopy analysis of SnO2under high pressure showesthat grain conduction is dominant in the whole electrical transport process, and thegrain resistance of SnO2decreases with the increase of pressure.4. The theoretical calculation of SnO2: according to the calculation results of bandstructure, we know, SnO2is always direct band gap semiconductors in the process ofthe whole pressure. The band gap of SnO2increases with pressure showed a trend ofincrease. The electrical state density distribution of SnO2shows that the valence bandis mainly occupied by4d states and5p state of Sn atom and2p state of O atom,2pstate of O atom plays a important role. The calculate results of the electrical statedensity distribution change little, indicating that the phase translation didn’t have toomuch impact for electrical stats density.In summary, we got the relationship of the electrical transport properties along withthe pressure. Though the synchrotron radiation X-ray diffraction spectrum and thetheoretical calculation results, we deeply analyzed the structural phase transition ofSnO2and the mechanism of the structural phase transition.