Stability and conductivity of Gd_2((Mo_(1/3)Mn_(2/3))_xTi_(1-x))_2O_7

摘要

A composite solid state electrochemical device, with (Gd_(1-x)Ca_x)_2Ti_2O_7 serving as the electrolyte and Gd_2(Ti_(1-x)Mo_x)_2O_7 (GT-Mo) as the anode has recently been proposed. The latter exhibits high levels of mixed cnduction under reducing atmospheres, but decomposes at high P_(O2). We have recently succeeded in extending the stability limits of the GT-Mo to higher P_(O2) with the addition of Mn. In this study, we report on the conductivity and stability of Gd_2((Mo_(1/3)Mn_(2/3))_xTi_(1-x))_2O_7 (GMMT) as a function of P_(O2), T, and composition utilizing impedance spectroscopy and x-ray diffraction. The addition of Mn extends the stability region of the material to P_(O2) = 1 atm with little change in the magnitude of the conductivity. Defect models explaining the dependence of the conductivity on oxygen partial pressure are presented. Preliminary results from the use of an electronic blocking sandwich cell used to isolate the ionic conductivity of GMMT are also presented.