Nonstoichiometry of Zr0.164Ce0.654Y0.182O1.91-delta

Nonstoichiometry of fluorite-type oxide solid solutions Zr0.164Ce0.654Y0.18 2O1.91-delta was measured as a function of temperature (T = 973-1273 K) and oxygen partial pressure (P (O-2) = 10(-2)-10(-24) atm) using thermogravime try. The experimental date was well reproduced by the regular solution mode l. From the delta-logP (O-2)-T relationship, the partial molar enthalpy (h( O) - h degrees(O)) and the partial molar entropy (s(O) - s degrees(O)) of o xygen in Zr0.164Ce0.654Y0.182O1.91-delta were also determined as a function of delta. The (S-O -S degrees(O)) agrees well with theoretical calculation using the random configuration. The delta dependence of (h(O) - h degrees( O)) can be attributed to origin of the deviation from ideal solution behavi or of this system.