Defect Structure of Ta2O5

Electrical conductivity, thermoelectric power, and weight change were measured for polycrystalline Ta 2 O 5 from 900° to 1400°C. The predominant ionic and electronic defects in this temperature range are oxygen vacancies and electrons. The oxygen‐vacancy and electron mobilities are 8.1 × 10 3 exp (−1.8 eV/ k T) and ∼0.05 cm 2 /V‐s, respectively. At O 2 partial pressures near 1 atm, the ionic‐defect concentration is essentially fixed by the presence of lower‐valence cation impurities, and the total electrical conductivity is predominantly ionic, whereas at low P o2 's the conductivity is electronic and proportional to P P o2 −1/6 .