Chemical expansion of La sub(0.8Sr) sub(0).2Fe sub(0.7Ga) sub(0).3O sub(3-[delta])

This paper deals with the chemical expansion measurements and modelling of La sub(0.8Sr) sub(0).2Fe sub(0.7Ga) sub(0).3O sub(3-[delta]. The expansion behavior has been evaluated using a dilatometer and X-ray diffraction over a wide range of temperatures (RT to 1373 K) and oxygen partial pressures (10[super]- 21 to 1 atm). The material stoichiometry evolution with temperature and oxygen partial pressure has been measured using thermogravimetry analysis at different oxygen partial pressure, from 10[super]- 21 to 0.5 atm and from RT to 1473 K. Considering a typical defect model for lanthanum ferrite oxides, chemical expansion depends linearly on the Fe[super]4+ concentration rather than on the oxygen vacancy concentration. A model of chemical expansion as a function of pO) sub(2) and temperature is then proposed. It helps to understand and anticipate the chemical expansion behavior exhibited by this material when used as Ionic Transport Membrane (ITM).