Synthesis and Triple Conductive Properties of Ba and Fe Co-Doped Sr2TiO4 Based Layered Perovskite: (BaxSr2-x) (Ti0.9Fe0.1)O4-δ (X= 0.05, 0.10)

This study investigated the effects of Ba substitution on protonic conductive properties in the Fe doped Sr2TiO4 layered perovskite. We synthesized sintered samples of (BaxSr2-x)(Ti0.90Fe0.10)O4-δ (x= 0.05, 0.10) (BSTF05, BSTF10). The result of X-ray diffraction suggests that solid solute limitation of Ba is between x= 0.05 and 0.10. BSTF05 at 600 °C shows proton and oxide-ion conductivities as well as elecronic conductivity. It means that BSTF05 is a triple conductor at 600 °C under oxidation atmosphere. The proton conductivities in BSTF05 are lower than that in Ba un-doped Sr2(Ti0.9Fe0.1)O4-δ evaluated in our previous work, suggesting that the effect of the Ba substitution on proton defect generation is small. The redox reaction of Fe ions is more important for creation of proton defects in the layered perovskites.

Computational investigation of Zn-doped and undoped SrEu2Fe2O7 as potential mixed electron and proton conductors

Density functional theory calculations are employed to investigate the formation and conducting behaviors of oxygen vacancies and proton defects in Ruddlesden–Popper oxide SrEu2Fe2O7.

Synthesis and characterization of BaSn(OH)6 and BaSnO3 acicular particles

The synthesis of BaSn(OH)6 acicular crystals by precipitation at 100 °C from aqueous solutions and their transformation in the perovskitelike compound BaSnO3 was investigated. Single acicular crystals 100–200 μm in length were obtained from a 0.05M solution, whereas bundlelike aggregates of 20–40 μm were precipitated from 0.2–0.6 M solutions. The x-ray diffraction pattern of barium hexahydroxostannate was indexed according to monoclinic symmetry with cell parameters a = 11.029 ± 0.002 Å, b = 6.340 ± 0.001 Å, c = 10.563 ± 0.001 Å = 128.51 ± 0.01°, α = γ = 90°. The BaSn(OH)6 particles decomposed to BaSnO3 and water at approximately 270 °C and the original morphology was retained. The resulting product had specific surface area up to 30–40 m2/g and consisted of 10–20 nm crystallites. The larger unit cell edge in comparison to the reference value and the continuous weight loss up to 1200 °C indicate that water is not completely released during decomposition and a substantial amount of proton defects (up to 0.4 mol per mole of BaSnO3) is incorporated in the perovskite lattice as OH− groups. Normal crystallographic properties of BaSnO3 are restored only after calcination at 1300 °C.

Proton Solubility in Undoped and Fe-doped SrTiO3: Temperature Dependence and Formation of Defect Associates

The temperature dependence of the solubility of proton defects in SrTiO3 single crystals was investigated by IR spectroscopy. Based on the integrated absorption of the OH stretching vibration bands, the enthalpies of the dissolution reaction were determined for undoped and Fe-doped SrTiO3. In contrast to undoped SrTiO3, which shows only one unique OH absorption frequency, characteristic sidebands were observed for Fe-doped crystals. These sidebands were attributed to the formation of associates between donor-type proton defects and Fe-acceptors in the perovskite lattice. From the temperature dependence of the sideband absorptions, an association enthalpy was estimated. The proton solubility and the sidebands were not affected by changing the oxygen partial pressure between approx. 10-15 and 105 Pa.