DEFECT STRUCTURE AND ELECTRICAL-CONDUCTIVITY STUDIES OF THULIUM SESQUIOXIDE

The electrical conductivity of thulium sesquioxide has been measured from 400 to 1100 degree C under oxygen partial pressures (P//o//2) of 10** minus **6 to 10** minus **1 atm. Plots of log conductivity vs 1/T at constant P//o//2 are found to be linear with an inflection point, the activation energies obtained from the slopes being 34. 5 kcal/mole in the higher temperature region and 19. 3 kcal/mole in the lower temperature region. The P//o//2 dependencies of the electrical conductivity are found to be linear and closely approximated by sigma varies directly as P//o//2**1**/**5**. **3 in the temperature range 600-1100 degree C and sigma varies directly as P//o//2**1**/**6**. **3 in the range 400-600 degree C. The dominant defect is V triple prime //T//m within the temperature region studied, but an ionic contribution exists in the lower temperature region. An interpretation of the conductivity dependences on temperature and P//o//2 is presented and conduction mechanisms are suggested to account for the data.