  In this paper we report an extensive neutron diffraction investigation at
high temperature on the BaCe0.80Y0.20O2.9 proton conducting material. Our
results precisely define the structural evolution of the compound as a function
of temperature which is from a monoclinic (room temperature) to a cubic (800C)
structure. Neutron data have been correlated to calorimetric measurements (TGA
and DSC) and conductivity properties of the material.
