Oxygen surface exchange of Y0.2Ce0.8O2-x under reducing atmosphere

Oxygen surface exchange was measured for Y0.2Ce0.8O2-x (YDC) and Y(0.1)5Zr( 0.85)O(2-y) (YSZ) over a wide range of oxygen partial pressures (7.3 X 10(- 21) to 0.17 bar) by isotope oxygen exchange (O-18/O-16) using secondary-ion mass spectrometry analysis at 973 K. Diffusion depth profiles of O-18 in Y DC and YSZ were analyzed by an appropriate fitting equation to calculate di ffusion coefficient (D) and surface exchange coefficient (k). The diffusion coefficients (D) for YDC and YSZ are consistent with the reference data. T he k values for both materials were similar (about k = 5-9 X 10(-8) cm s(-1 )) at the same temperatures. The k value increases with decreasing oxygen p artial pressure for both YDC and YSZ. A relationship between the k value an d the concentrations of electron and oxygen vacancy is discussed. (C) 1998 The Electrochemical Society, Inc. S1099-0062(97)12-036-3.