OXYGEN NONSTOICHIOMETRY AND DEFECTS IN MN-DOPED GD2TI2O7+X

The oxygen nonstoichiometry in Mn-doped Gd2Ti2O7, Gd-2(Ti0.975Mn0.025) (2)O-7+x, was measured electrochemically, as a function of temperature and oxygen partial pressure, with the aid of an oxygen titration cell . The analysis of the data shows that the defect equilibrium can be de scribed by considering the dominant point defects to be neutral oxygen interstitials, doubly charged oxygen vacancies, and trivalent and qua drivalent Mn ions substituted in the Ti sites. The enthalpies for the formation of neutral oxygen interstitials and trivalent Mn are determi ned.