Nonstoichiometry of Zr<sub>0.l64</sub>Ce<sub>0.654</sub>Y<sub>0.l82</sub>O<sub>1.91-</sub><i><sub>δ</sub></i>

Nonstoichiometry of fluorite一敏pe oxide solid solutions Zro．164Ceo．654Yo，18201．g1一δwas measured as a function of temperature(T＝973-1273K)and oxygen partial pressure(P(02)＝10-2-10 24atm)using thermogravimetry．The experimen一 ぬ1date was well reproduced by the regular solution mode1、From theδ一logP(02)一T relationship，the partial molar enthalpy(ho-hる)andthepa翻molaren柱opy(so-sろ)ofo》ΨgeninZro．164Ceo．654Yo．18201．gl一δwere飢so deteminedas a 血nction ofδ．The(so-s＆)agrees well with theoretical calculadon using the random con五guradon．Theδdependence of(ho-hる)can be attributed to origin of the deviation from ideal solution behavior of this system．