Oxyhydrides of (Ca,Sr,Ba)TiO₃ Perovskite Solid Solutions

The oxyhydride solid solutions (Ca,Sr)­TiO_3–<i>x</i>H_<i>x</i> and (Sr,Ba)­TiO_3–<i>x</i>H_<i>x</i> have been prepared by reducing the corresponding ATiO₃ oxides with calcium hydride. Under the reaction conditions examined, a hydride content of <i>x</i> = 0.1–0.3 was obtained for all compositions. Compared to our previous result with BaTiO_3–<i>x</i>H_<i>x</i>, the larger particle size in this study (20–30 μm vs 170 nm) resulted in a somewhat lower hydride amount despite prolonged reaction times. We examined changes in cell volume, octahedral tilt angle, and site occupancy of different anion sites after conversion to oxyhydrides; it appears that these oxyhydrides fit the geometrical descriptions typical for regular ABO₃ perovskites quite well. The hydrogen release temperature, previously shown to be indicative of the hydride exchange temperature, however, does not scale linearly with the A-site composition, indicating a potential effect of chemical randomness