Abstract
A novel method for performing in situ characterization of the electrical properties of pristine, ultrafine nanopowders is reported. A modified dilatometer, with a spring‐loaded push rod and electrodes, allows for the simultaneous monitoring of the packed nanopowder's lateral displacement as well as its complex impedance spectroscopy as a function of temperature within a controlled environment. Anatase TiO2 quantum dots of 2 nm diameter, on average, are examined and found to simultaneously shrink and become more resistive upon initial heating. The resistance changes by approximately 3 orders of magnitude upon heating, associated with the desorption of adsorbed water, demonstrating the need for sample preconditioning. Subsequent electrical resistivity measurements, as a function of oxygen partial pressure, over approximately 40 orders of magnitude, at temperatures between 300 °C and 400 °C, exhibit nearly 9 orders of magnitude change in conductivity. The data are consistent with a Frenkel‐based defect disorder model characterized by an enthalpy of reduction of 5.5 ± 0.5 eV.
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