The oxide-ion conductivity of NdBaInO 4 has been increased by Sr doping. Nd 0.9 Sr 0.1 BaInO 3.95 showed the highest electrical conductivity among Nd 1Àx Sr x BaInO 4Àx/2 (x ¼ 0.0, 0.1, 0.2, and 0.3). The oxide-ion conductivity s ion of Nd 0.9 Sr 0.1 BaInO 3.95 (s ion ¼ 7.7 Â 10 À4 S cm À1 ) is about 20 times higher than that of NdBaInO 4 (s ion ¼ 3.6 Â 10 À5 S cm À1 ) at 858 C, and the activation energy of oxide-ion conduction is a little lower for Nd 0.9 Sr 0.1 BaInO 3.95 (0.795(10) eV) than that for NdBaInO 4 (0.91(4) eV). The structure analysis based on neutron powder diffraction data revealed that the Sr exists at the Nd site and oxygen vacancies are observed in Nd 0.9 Sr 0.1 BaInO 3.95 . This result indicates that the increase of the oxide-ion conductivity is mainly due to the increase of the carrier concentration. The bond valence-based energy landscape indicated two-dimensional oxide-ion diffusion in the (Nd,Sr) 2 O 3 unit on the bc-plane and a decrease of the energy barrier by the substitution of Nd with Sr cations. † Electronic supplementary information (ESI) available: A document containing the crystallographic data of Nd 0.9 Sr 0.1 BaInO 3.95 , additional experimental information, and a crystallographic information le (CIF) of Nd 0.9 Sr 0.1 BaInO 3.95 . See

The potential of calcium-doped layered perovskite compounds, BaNd 1– x Ca x InO 4– x /2 (where x is the excess Ca content), as protonic conductors was experimentally investigated. The acceptor-doped ceramics exhibit improved total conductivities that were 1–2 orders of magnitude higher than those of the pristine material, BaNdInO 4 . The highest total conductivity of 2.6 × 10 –3 S cm –1 was obtained in the BaNd 0.8 Ca 0.2 InO 3.90 sample at a temperature of 750 °C in air. Electrochemical impedance spectroscopy measurements of the x = 0.1 and x = 0.2 substituted samples showed higher total conductivity under humid environments than those measured in a dry environment over a large temperature range (250–750 °C). At 500 °C, the total conductivity of the 20% substituted sample in humid air (∼3% H 2 O) was 1.3 × 10 –4 S cm –1 . The incorporation of water vapor decreased the activation energies of the bulk conductivity of the BaNd 0.8 Ca 0.2 InO 3.90 sample from 0.755(2) to 0.678(2) eV in air. The saturated BaNd 0.8 Ca 0.2 InO 3.90 sample contained 2.2 mol % protonic defects, which caused an expansion in the lattice according to the high-temperature X-ray diffraction data. Combining the studies of the impedance behavior with four-probe DC conductivity measurements obtained in humid air, which showed a decrease in the resistance of the x = 0.2 sample, we conclude that experimental evidence indicates that BaNd 1– x Ca x InO 4– x /2 is a fast proton conductor.

Overbonding of the channel oxygens in the apatite-type lanthanum silicates was found to be a key for the high oxide-ion conductivities by the present single-crystal neutron and X-ray diffraction studies.

Critical to the development of solid electrolytes in clean energy applications is a new class of proton conductors. Here, we report the first example of proton conductors belonging to (110)...

BaNdInO 4 is a new structure family of oxide-ion conductors. In the present work, we have investigated the crystal structure and electrical conductivity of Ba 1+x Nd 1−x InO 4−x/2 where x is the excess Ba content. It was found that Ba 1.1 Nd 0.9 InO 3.95 shows (i) about 12 times higher oxide-ion conductivity at 858 • C and (ii) a little lower activation energy for oxide-ion conduction than BaNdInO 4 . The higher oxide-ion conductivity of Ba 1.1 Nd 0.9 InO 3.95 is mainly ascribed to higher carrier concentration. Careful structure analyses using both the single-crystal X-ray diffraction and time-of-flight (TOF) neutron powder diffraction data enabled to determine the position of excess Ba cation and occupancy factor of O anion. It was found that the excess Ba cation substitutes for Nd cation and that oxygen vacancies exist in Ba 1.1 Nd 0.9 InO 3.95 . The refined occupancy factor of oxygen atom 0.9829( 17) indicates the higher concentration of oxygen vacancies in Ba 1.1 Nd 0.9 InO 3.95 , compared with BaNdInO 4 , giving higher oxide-ion conductivity in Ba 1.1 Nd 0.9 InO 3.95 . The larger-sized Ba substitution for Nd cation makes the bottleneck size larger, leading to the lower activation energy. The bond valence-based energy landscape calculated for the refined crystal structure of Ba 1.1 Nd 0.9 InO 3.95 at 800 and 24 • C indicated two-dimensional oxide-ion diffusion in the A rare earth oxide (Nd,Ba) 2 O 3 unit on the bc plane.

Mg3TeO6-type Ca0.8Y2.4Sn0.8O6 has been found as a new structure family of oxide-ion conductors. From bond-valence-based energy (BVE) calculations for 147 compositions, which contain tin (Sn) as an essential element, Mg3TeO6-type Ca0.8Y2.4Sn0.8O6 was found to have a low energy barrier for oxide-ion migration. Ca0.8Y2.4Sn0.8O6 was synthesized by the solid-state reaction, and its electrical conductivity and crystal structure were investigated. The total electrical conductivity at various partial oxygen pressures and band gap estimated from the UV-vis spectrum suggested that Ca0.8Y2.4Sn0.8O6 is a pure oxide-ion conductor. The activation energy for the oxide-ion conductivity of Ca0.8Y2.4Sn0.8O6 was 1.39(4) eV. Synchrotron X-ray powder diffraction data of Ca0.8Y2.4Sn0.8O6 at 300 and 1273 K were successfully analyzed with the Mg3TeO6-type structure. The BVE calculation using the refined crystal structure of Ca0.8Y2.4Sn0.8O6 at 1273 K strongly suggested three dimensional oxide-ion diffusion.

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Brownmillerite CaFeO (CFO) exhibits a magnetic transition at T ∼ 730 K. Many studies have reported the magnetic properties of CFO. However, the magnetic structure of CFO is still debated, i.e., whether the magnetic ordering is purely antiferromagnetic or weakly ferromagnetic, which originated from canted magnetic moments. In addition, the reason for the CFO showing large magnetoresistance is still unclear. This study attempts to address the unresolved issues stated above by multiple investigations on the crystal structure, magnetization, and Mössbauer parameters. Based on the results of the investigation, we conclude that the CFO is not purely antiferromagnetic but weakly ferromagnetic. That is the reason for the disappearance of the spontaneous magnetization at the magnetic critical temperature T. The Mössbauer spectroscopy shows that the magnetic moments slightly cant against the a-direction, resulting in the presence of a net magnetic moment along the c-direction under the space group of Pnma. A reason for the canted magnetic moments is due to the presence of the Dzyalosinskii-Moriya (DM) interaction. The electric field gradient (EFG) refined from the Mössbauer spectroscopy investigated at 287 K is larger than that at 750 K, which is higher than T. This suggests that the EFG changes below T. A local electric polarization induced by the DM interaction is a possible reason for the change in the EFG. As a result, strong correlations between the magnetic ordering and the electrical properties appear in the CFO. The Arrhenius plot of the total electrical conductivity showed a kink at T, which is one of these strong correlations.