Impedance spectroscopy and DSC studies on nanostructured SnO2

Nanocrystalline tin oxide (SnO2) was prepared by the inert gas condensation technique (IGCT) using an ultra-high vacuum (UHV) chamber and chemical precipitation technique developed in-house. The samples were characterised by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impedance spectroscopy. A brief description about the development of a UHV chamber is also given. The XRD results show that there is a possibility of existence of a high-pressure orthorhombic phase when the IGCT sample is annealed. Pure tetragonal SnO2 is obtained by a chemical precipitation method. DSC result shows oxidation of tin, when the average grain size is very small. The impedance plots show a decrease in resistance with increase in temperature when the grain size is less than 6 nm. However, in the case of materials deposited in pure tin form, resistance increases with increase in temperature due to oxidation. The variations of dc conductivities and activation energies have been studied in both methods of preparation.