Defect structure and electrical conductivity of pure and doped lutetium sesquioxides

Abstract

Pure Lu 2O 3 and Lu 2O 3-CaO solid solutions containing 1, 5 and 10 mol % CaO were prepared and found to have the rare earth-type cubic structure by X-ray diffraction technique. Electrical conductivities were measured as a function of temperature from 600 to 1100°C and of P o 2 from 10 −5 to 2 × 10 −1atm. The defect structures, type of semiconductor and the electrical conduction mechanisms were deduced from the results. The temperature dependence of the electrical conductivities shows different behaviors for pure and doped Lu 2O 3, showing different activation energies, 1.92 and 1.58 eV, respectively. The 1 n values in σαP 1 n o 2 are 1 n = 1 6 and 1 n = 1 4 for pure and doped Lu 2O 3 at P o 2s higher than 10 −4 and 10 −3 atm, respectively. From the variation of the 1 n values from 1 n ≅ 0 to 1 n = 1 6 or 1 n = 1 4 , ionic and electronic conduction mechanisms are suggested in the low- and high-oxygen partial pressure regions with two possible defect models.