Characterization and creep properties of proton-conducting Yb-doped barium cerate

Polycrystals of Yb-doped barium cerate with composition BaCe0.95Yb0.05O3−δ have been synthesized via a solid-state reaction route. The ceramic has a single orthorhombic perovskite phase, and the crystallographic unit cell is almost unperturbed with respect to undoped BaCeO3. The compound exhibits a homogeneous distribution of equiaxed and submicron grains. The high-temperature mechanical properties have been studied for the first time. Mechanical tests were carried out in compression between 1100 and 1250 °C in air at constant initial strain rate. A gradual brittle–ductile transition was observed with increasing temperature and/or decreasing strain rate. Grain boundary sliding is the main deformation mechanism in the ductile region. In this regime, the true stress–true strain curves display an unusual behavior, with an initial strength drop followed by an extensive steady-state stage. This behavior is accompanied by the emergence of new, fine grains along the boundaries and triple junctions of the original grains during deformation.