Defects and charge transport in stabilized α-Ta2O5

Abstract

Abstract The high temperature form of tantalum oxide, α-Ta2O5, stabilized by the addition of several mol% SC2O3, has been shown to be an excellent oxygen conductor. Lattice oxygen transport is comparable to that found in calcia stabilized zirconia in the temperature range 500-950° and is 1 -2 orders of magnitude greater than found for low (β) Ta2O5 at these temperatures. Electrical conductivity is characterized by a dominant ionic component with an activation energy, in air, ∼1 eV. n-type electronic conduction, characterized by a po2 −1/4 dependence, becomes important at highly reduced oxygen partial pressures and high temperatures. Transport properties have been characterized using complex impedance measurements within the kinetically stable range of α-Ta2O5, at 500 po 2>10−20 atm; and within the thermodynamically stable temperature range, T>1360°. Frequency range of measurement was 10 Hz-2 MHz. Galvanic cell measurement of ionic transference number was used to confirm oxygen vacancies as the d...