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Perovskite-type Nd0.75Ba0.25Co0.8Fe0.2O3-δ (NBCF25) was prepared via solid-state synthesis method at 1300 °C in air. Powder X-ray diffraction showed the formation of a single-phase orthorhombic phase in the Pnma space group. It showed minor reactivity with Sr and Mg-co-doped lanthanum gallate (LSGM) when sintered with 30 wt.% LSGM at 1050 °C. 4-probe DC chronopotentiometry measurements were performed on the sintered sample pellets and showed a maximum conductivity of 674 S/cm at 700 °C. 2-probe AC electrochemical impedance spectroscopy measurements were performed on LSGM pellets from 650 to 800 °C to investigate the oxygen reduction property of NBCF25 using a composite slurry (70 wt.% NBCF and 30 wt.% LSGM). It showed the lowest area-specific resistance of 0.07 Ω cm2 at 800 °C in air. Impedance spectroscopy genetic programming was used to understand the oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

[sup.139]La solid-state NMR spectra, acquired at 21.1 and 11.7 T, have been used to evaluate the structural properties of the lithium ion battery materials, [La.sub.32][Li.sub.16][Fe.sub.6.4][O.sub.67] and [Li.sub.3x][La.sub.2/3- x]Ti[O.sub.3]. In particular, atomic-level disorder in the second coordination sphere environment of lanthanum in these materials has been indicated by the observation of a distribution in the asymmetry parameters and the quadrupolar coupling constants derived from experimental NMR spectra, and supported by theoretical calculations. For comparison, [sup.139]La NMR has been obtained for the two model compounds [La.sub.2][O.sub.3] and LaNb[O.sub.4], in which there is no atomic-level disorder. Quadrupolar coupling constants in the range of 17 to 59 MHz have been measured, and these values are supported by previous work as well as theoretical predictions performed in CASTEP. It has been shown that [sup.139]La NMR is a useful tool for the structural analysis of lithium ion battery materials, and when combined with [sup.7]Li MAS NMR and powder X-ray diffraction, can be used to determine the structure of complex solid-state electrolyte and electrode materials. Key words: NMR, quadrupolar nuclei, lithium ion batteries, [sup.139]La. On a utilise les spectres RMN du [sup.139]La a l'etat solide, acquis a 21,1 et 11,7 T, pour evaluer les proprietes structurales des materiaux ioniques du lithium utilises pour les batteries, [La.sub.32][Li.sub.16][Fe.sub.6.4][O.sub.67] et L13x[La.sub.2/3-x]Ti[O.sub.3]. En particulier, un desordre au niveau atomique dans la deuxieme sphere de coordination de l'environnement du lanthane de ces materiaux a ete mis en evidence par l'observation d'une distribution dans les parametres d'asymetrie et dans les constantes de couplage quadripolaire obtenues a partir des spectres RMN experimentaux et confirmees par des calculs theoriques. A des fins de comparaison, on a aussi determine les spectres RMN du [sup.139]La de deux composes modeles, [La.sub.2][O.sub.3] et LaNb[O.sub.4], dans lesquels on n'observe aucun desordre au niveau atomique. On a mesure des constantes de couplage quadripolaire de l'ordre de 17 et 19 MHz; ces valeurs sont en accord avec celles rapportees dans un travail anterieur et elles correspondent aux valeurs calculees par le programme CASTEP. On a demontre que la RMN du [sup.139]La est un outil utile pour l'analyse structurale des materiaux ioniques du lithium utilises dans les batteries et que, lorsque combinee avec la RMN avec rotation a l'angle magique (RAM) et la diffraction des rayons-X, elle peut etre utilisee pour determiner la structure d'electrolytes complexes a l'etat solide et de materiaux d'electrode. Mots-cles : RMN, noyau quadripolaire, batteries aux ions lithium, [sup.139]La. [Traduit par la Redaction] Introduction, Lithium ion batteries play an important role in the development of environmentally friendly energy sources. (1) With applications in many portable electronic devices, lithium ion batteries are sought after in [...]

We report the synthesis, crystal structure, and electrochemical properties of new Fe-doped [Ba.sub.2]([Ca.sub.1-x-y][Fe.sub.x][Nb.sub.y]) ([Nb.sub.1-z][Fe.sub.z])[O.sub.6-δ] (Fe-BCN). The Fe-BCN was synthesized by a solid-state method in air using corresponding metal oxides and salts at elevated temperature. All of the observed powder X-ray diffraction (PXRD) peaks of the investigated Fe-BCN were indexed as cubic Fm-3m (space group No. 225) double perovskite-type structure with cell constants a ~ 8.4 Å and is consistent with selected area electron diffraction (SAED). Rietveld analysis suggested the distribution of Fe was at both 4a and 4b sites, supported the proposed chemical formula [Ba.sub.2]([Ca.sub.1-x-y] [Fe.sub.x][Nb.sub.y])([Nb.sub.1-z][Fe.sub.z])[O.sub.6-δ]. This was further verified by bond valence sum (BVS) analysis of the cations. The Fe-BCN showed superior chemical stability in pure C[O.sub.2] and boiling [H.sub.2]O confirmed by PXRD and FTIR. The electrical conductivity was determined by AC impedance spectroscopy. Among the samples investigated, [Ba.sub.2]([Ca.sub.0.79][Fe.sub.0.21])([Nb.sub.0.71][Fe.sub.0.29) [O.sub.6-δ] showed the highest total (bulk + grain-boundary) conductivity of 1.1 x [10.sup.-2] S [cm.sup.-1] in humidified (3%) [N.sub.2] at 600°C with activation energy of 0.43 eV in the temperature range 200-800°C. Key words: protonic conductors, perovskites, Fe-BCNs, mixed ionic and electronic conductors (MIECs), solid oxide fuel cells (SOFCs), anodes, Rietveld refinement, AC impedance spectroscopy, selected area electron diffraction (SAED), powder X-ray diffraction (PXRD). On a effectue la synthese, determine la structure cristalline et mesure les proprietes electrochimiques de nouveaux [Ba.sub.2]([Ca.sub.1-x-y][Fe.sub.x][Nb.sub.y])[O.sub.6δ] dopes au fer (Fe-BCN). Les Fe-BCN ont ete synthetises par une methode a l'etat solide, dans l'air, en utilisant les oxydes et des sels des metaux correspondants, a des temperatures elevees. Toutes les raies des spectres de diffraction des rayons-X de poudres (DRXP) des Fe-BCN etudies ont ete indexees comme des structures cubiques Fm-3m (groupe d'espace No. 225) de type perovskite double avec des constantes de maille de α ~ 8,4 Å qui est en accord avec la diffraction electronique d'une surface choisie (DESC). Une analyse de Rietveld suggere que la distribution du Fe se fait tant sur les sites 4a que 4b qui est en accord avec la formule chimique proposee [Ba.sub.2]([Ca.sub.1-x-y][Fe.sub.x])([Nb.sub.y])[O.sub.6-δ]. Cette hypothese a aussi ete confirmee par une analyse de la somme des valences de liaison (SVL) des cations. La stabilite chimique superieure du Fe-BCN dans le C[O.sub.2] pur et dans l'eau bouillante a ete confirmee par DRXP et par infrarouge a transformee de Fourier (IR-TF). On a determine la conductivite electrique par spectroscopie d' impedance en courant alternatif (CA). Parmi les echantillons etudies, le [Ba.sub.2]([Ca.sub.0,79][Fe.sub.0,21]) ([Nb.sub.0,71][Fe.sub.0,29])[O.sub.6-δ] presente la conductivite totale (ensemble + limite des grains) la plus elevee, 1,1 x [10.sup.-2] S [cm.sup.-1], dans de l'azote humidifie (3 %), a 600°C, avec une energie d'activation de 0,43 eV dans la plage de temperature allant de 200 a 800°C. Mots-cles : conducteurs protoniques, perovskite, Fe-BCN, conducteurs mixtes ionique et electronique (CMIE), piles a combustible a oxyde solide (PCOS), anodes, affinement de Rietveld, spectroscopie d'impedance a courant alternatif, diffraction electronique d' une surface choisie (DESC), diffraction des rayons X de poudres (DRXP)., Introduction Proton conduction in the perovskite-type (AB[O.sub.3] A = divalent or trivalent metal ions; B = trivalent or tetravalent metal ions) oxide was pioneered by Iwahara et al. (1) in [...]

Among the alkaline earth-based perovskite oxides, the Ba-based perovskites have superior chemical stability and tunable electrical/catalytic property via chemical substitution/doping. One of the best-known examples is Ba3Ca1.18Nb1.82O8.73 as a ceramic proton conductor for all-solid-state steam electrolysis and solid oxide fuel cells (SOFCs). Structural ordering variation is often driven by chemical composition, which directly correlates with their chemical/physical properties. In the present work, we develop a comprehensive functional perovskite-type phase diagram for the Ba–Ca–Ta–O quaternary system Ba3Ca1+xTa2−xO9−3x/2 (0 ≤ x ≤ 0.36) with a wide chemical composition between 1000 and 1550 °C, coupled with theoretical calculations to investigate the cation ordering in supercells. Furthermore, the impact of cation clustering on the diffusion pathways of O2− ions was evaluated as a case study. Experimentally, precise cation ordering and other structural features are quantitively determined by TOF-neutron and synchrotron X-ray diffraction analyses. This work provides a comprehensive evaluation of some potential applications of the Ba–Ca–Ta–O quaternary system. The electrochemical impedance data were also systematically studied by impedance spectroscopy genetic programming (ISGP). The electrical conductivity was found to increase from x = 0 to x = 0.27 and then decrease for the end member when x = 0.36 due to a decrease in mobile charge carrier concentration. Interestingly, in dry air, the electrical conductivity was found to increase from x = 0 to x = 0.36. However, only Ba3Ca1.18Ta1.82O8.73 (BCT18) and Ba3Ca1.27Ta1.73O8.595 (BCT27) were found to show an increasing trend in conductivity in humid atmospheres, and this indicates that the clustering effect was pO2 dependent. [ABSTRACT FROM AUTHOR]