High-temperature mechanical behavior of proton-conducting yttrium-doped barium zirconate perovskite

The high-temperature mechanical properties of yttrium doped barium zirconate obtained by two different routes are reported in this work. Polycrystals with composition BaZr_0.85Y_0.15O_2.925 have been fabricated from nanopowders synthesized by a modified EDTA-citrate complexing method and conventionally sintered at 1600 °C for 24 h. The material exhibits a single cubic perovskite phase, with a homogeneous, dense and fine-grained microstructure consisting of equiaxed grains with an average size of 0.2 μm. Mechanical tests were carried out in compression between 1100 and 1325 °C in air at constant initial strain rate and at constant load. As the temperature increases and/or the strain rate decreases, a gradual transition from brittle-to-ductile behavior was found. In the brittle regime, the fracture is governed by an intergranular failure mode. In the ductile region, grain boundary sliding is the main deformation mechanism, characterized by a stress exponent of 2 and an activation energy of 570 kJ/mol.