Different defects formation modes under sevier reducing condition in primitive cubic perovskites, BaZr1-xYxO3-x/2 and BaSn1-xYxO3-x/2
March 10-14, 2019
Reduction processes using metal hydride agents modify the chemical and structural properties of metal oxide crystals with different manners, depending on the host crystals and the process conditions . In BaTiO3, a reduction using CaH2 leads to partial and random substitution of H-for the O2-site, which is compensated by a formal valence change of Ti4+ to Ti3+, imparting an electronic conduction  (Fig. 1a). In contrast, a low temperature reduction of SrFeO3 preferentially eliminates O2-at axial sites in the FeO6 octahedra without the H--incorporation to convert to SrFeO2 with a unique planner four-coordinated Fe2+  (Fig. 1b). An intermediate result has been obtained in a layered perovskite, LaSrCoO4, in which H- ions are selectively incorporated in specific O2- sites to form trans-configuration of H-ions . Herein, we focus on the metal hydride-reduction of BaZr1-xYxO3-x/2 (BZY) and BaSn1-xYxO3-x/2 (BSY) and relevant defect chemistry. Both system have the primitive cubic perovskite structure and are popular fast protonic conductor. The latter is related to our expectation that the H-ions are incorporated with a similar manner with the OH- formation via OOX + VO·· + CaH2 ® 2HO· + CaO. BZY and BSY powders were annealed in vacuum-sealed glass tubes containing metal hydride agents at 350-550 °C.
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Katsuro Hayashi, Hiroshi Watanabe, Hirofumi Akamatsu, and George Hasegawa, "Different defects formation modes under sevier reducing condition in primitive cubic perovskites, BaZr1-xYxO3-x/2 and BaSn1-xYxO3-x/2" in "Nonstoichiometric Compounds VII", ECI Symposium Series, (2019). https://dc.engconfintl.org/nonstoichiometric_vii/53