Combined Neutron and Synchrotron X-ray Diffraction investigation of the BaCe(0.85-x)Zr(x)Y(0.15)O(3-delta) (0.1 <= x <= 0.4) Proton Conductors

In this paper we investigated, by means of combined neutron and X-ray synchrotron diffraction, the structural properties of the BaCe(0.85-x)Zr(x)Y(0.1.5)O(3-delta) solid solution as a function of Zr-doping (0.1 <= x <= 0.4) and temperature. Compositions within this system have been proposed as electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC) due to their significant proton conductivities. However, no systematic investigations of the crystal structure evolution as a function of temperature have been reported in the literature. In this paper, we could define the phase stability up to 800 degrees C for each member of the BaCe(0.85-x)Zr(x)Y(0.1.5)O(3-delta) solid solution showing that for lower Zr-doping levels (x = 0.1 and 0.2) four different crystal structures are found in the T-range investigated. For higher Zr-doping levels (x = 0.3 and 0.4), the samples show a more symmetric structure already at room temperature (rhombohedral symmetry) and pass through two phase transitions. The exact knowledge of the structural features as a function of temperature is an essential piece of information in order to assess the possible use of these electrolyte materials in real devices.