Pressure dependence of the electrical resistivity of natural cassiterite SnO_2 and of undoped and Co-doped nanocrystalline SnO_2

摘要

The pressure dependence of the electrical resistivity of three different samples of cassiterite, namely natural cassiterite SnO_2, synthetic nanocrystalline SnO_2 (with crystallite size 46 nm) and nanocrystalline Co-doped SnO_2 (with crystallite size 32 nm), has been measured up to 7 GPa at room temperature. The resistivity of natural cassiterite SnO_2 decreases from 2.5×10~4?m at normal pressure and temperature to 1.7×10~4?m at 7.0 GPa. The nanocrystalline SnO_2 has a high resistivity 6.0 × 10~5?m at normal pressure and temperature and decreases with pressure reaching a value of 2.98 × 10~5?m at 7 GPa. The activation energy of the electrical conduction of the studied samples were found to be 0.32 eV for the natural SnO_2, 0.40 eV for the nanocrystalline SnO_2 sample and 0.28 eV for the nanocrystalline Co-doped SnO_2. Measurements of the pressure dependence of the electrical resistivity of the Co-doped SnO_2 showed a decrease from 3.60 × 10~5 to 5.4 × 10~4?m at 7.0 GPa. We did not observe any pressure-induced phase transition in SnO_2 up to 7 GPa. This study of the high-pressure phase stability of cassiterite corroborates the experimental findings of SnO_2 nanoinclusions in diamonds.