Combined Neutron and Synchrotron X-ray Diffraction Investigation of the BaCe_0.85-xZr_xY_0.15O_3-δ (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 0.15 O 3-δ 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 °C for each member of the BaCe 0.85- x Zr x Y 0.15 O 3-δ 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.