The conductivity of Gd2Sn2O7 was measured as a function of temperature, O partial pressure and Ca dopant concentration, and an effective Frenkel constant and O vacancy mobility were deduced. A high observed degree of intrinsic anion disorder was consistent with the predicted effect of the cation radius ratio in such pyrochlore compounds. Similar measurements were made of the solid solutions, Gd2(Ti1-xSnx)2O7 and Gd2(Zr1-xSnx)2O7, and an intrinsic anion disorder was found to be related to the x-value or the cation radius ratio. Systematic decreases in O vacancy mobility with increasing Sn content were observed.

T.Yu, H.L.Tuller: Solid State Ionics, 1996, 86-88[1], 177-82