Stability and conductivity of Gd2((Mo1/3Mn2/3)xTi1-x)2O7

A composite solid state electrochemical device, with (Gd1-xCax)(2)Ti2O7 serving as the electrolyte and Gd-2(Ti1-xMox)(2)O-7 (GT-Mo) as the anode has recently been proposed. The latter exhibits high levels of mixed conduction under reducing atmospheres, but decomposes at high P-O2. We have recently succeeded in extending the stability limits of the CT-Mo to higher P-O2 with the addition of Mn. In this study, we report on the conductivity and stability of Gd-2((Mo1/3Mn2/3)(x)Ti1-x)(2)O-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.