Continuous Hydrothermal Synthesis in Supercritical Conditions As a Novel Process for the Elaboration of Y-doped BaZrO3

The present work describes a novel process for the elaboration of a ceramic material. Y-doped barium zirconate, an electrolyte material for Protonic Ceramic Fuel cell, was synthesized by a continuous hydrothermal process in supercritical conditions (410 degrees C/30.0 MPa) using nitrate precursors and NaOH reactants. The use of supercritical water allowed the formation of particles of about 50 nm in diameter with a narrow size distribution. X-Ray Diffraction examination revealed that a major perovskite phase with few BaCO3 and YO(OH) impurities was obtained. BaCO3 is assumed to form due to faster kinetics than Y-doped BaZrO3 resulting in a Ba-deficient perovskite phase. The Ba-deficiency limits the incorporation of yttrium into the perovskite structure. However, a thermal treatment at 1000 degrees C for 1 h allows to homogenize the composition and thus to obtain the compound Ba1.01Zr0.85Y0.15O3-delta.