NaLiMO(CO) (M = W and Mo): An Alternative Electrolyte for High-Temperature Electrochemical Cells.

Two new acentric oxycarbonates NaLiMO(CO) (M = W and Mo) were synthesized via a conventional solid-state route. Their structure was determined from X-ray diffraction data on single crystals. NaLiMO(CO) (M = W and Mo) crystallizes in the acentric cubic -43 space group ( ≈ 7.

Structural Characterization and Influence of Defects on the Optical Properties of the Oxygen-Deficient Perovskite BaLiNbO□.

A new oxygen-deficient perovskite BaLiNbO□ was synthesized via a conventional solid-state route and compared to the already known perovskite BaLiNbO. The structure of BaLiNbO□ was investigated by means of X-ray and neutron diffraction, TEM, NMR, and XPS. The study of its thermal behavior revealed an unexpected color change when heated to 1400 °C in a sealed platinum tube, with conservation of the initial X-ray structure.

CO Capture by NaTeO: Structure of NaH TeO and Kinetic Aspects.

β-NaTeO is able to trap CO in a humid atmosphere due to a partial Na/H exchange and the formation of NaHCO. The RT powder X-ray diffraction pattern of the resulting NaH TeO shows broad and narrow hkl lines preventing the structural study. We show by the DIFFaX program that Na/H exchange is topotactic since the structure, as in the mother form, consists of [TeO] chains of TeO octahedra.

β-NaTeO: Phase Transition from an Orthorhombic to a Monoclinic Form. Reversible CO Capture.

The present work concerns the tellurate NaTeO which has a 1D structure and could then present a CO capture ability. It has been synthesized in a powder form via a solid-state reaction and structurally characterized by thermal X-ray diffraction experiments, Raman spectroscopy, and differential scanning calorimetry. The room temperature structure corresponds to the β-NaTeO orthorhombic form, and we show that it undergoes a reversible structural transition near 420 °C toward a monoclinic system.

Preparation-Dependent Composition and O/F Ordering in NbOF and TaOF.

Through an analysis combining powder XRD, TGA, and F and H solid-state NMR, it is confirmed for NbOF and shown for TaOF that both contain hydroxyl defects and metal vacancies when prepared by aqueous solution synthesis. The formulations M□O(OH,F) of both the samples are determined. The effects of the usually applied thermal treatments are examined.

Instability of the Ionic Conductor LiBaLaBO (B = Nb, Ta): Barium Exsolution from the Garnet Network Leading to CO Capture.

The instability of the two garnets LiBaLaBO (B = Nb, Ta) has been studied on samples prepared in powder form by solid-state reaction. For this study, we coupled different techniques: powder X-ray diffraction, IR spectrometry, thermal analysis, transmission electron microscopy, and complex impedance spectroscopy. We showed that in ambient air and at low temperature (<150 °C), a spontaneous Li/H exchange occurs.

Phase Transitions in the Ruddlesden-Popper Phase Li2CaTa2O7: X-ray and Neutron Powder Thermodiffraction, TEM, Raman, and SHG Experiments.

The structure of the Ruddlesden-Popper layered perovskite Li2CaTa2O7, known for its high photocatalytic water activity since its discovery in 2008, is reinvestigated. This oxide has been characterized by powder X-ray and neutron thermodiffraction, TEM, second harmonic generation (SHG), and Raman experiments on powders and single crystals. It is shown that it undergoes two structural phase transitions (i) around 220 °C, mainly characterized by the progressive emergence of SHG signal at low temperatures, and (ii) at 660 °C, mainly characterized by changes of the temperature behavior of lattice parameters and by the emergence of Raman signals that linearly increase on decreasing temperature.

Fluoride solid electrolytes: investigation of the tysonite-type solid solutions La1-xBaxF3-x (x < 0.15).

Pure tysonite La1-xBaxF3-x solid solutions for x < 0.15 were prepared by solid state synthesis in a platinum tube under an azote atmosphere with subsequent quenching for 0.07 ≤x < 0.

Thermal structural characterization of the acentric layered perovskite LiHSrTa2O7: X-ray and neutron diffraction, SHG and Raman experiments.

The present work concerns the thermal structural characterization of the acentric Ruddlesden-Popper LiHSrTa2O7. A previous study, performed with powder neutron diffraction data, has revealed that at room temperature, LiHSrTa2O7 crystallizes in the Ama2 space group and that the acentric character is mainly due to the unequal distribution of the Li(+) and H(+) cations on their sites. In this new paper, the thermal behaviour has been studied by several techniques: powder X-ray and neutron diffraction, SHG experiments and Raman spectroscopy.

Reinvestigation of the total Li(+)/H(+) ion exchange on the garnet-type Li5La3Nb2O12.

Li(+)/H(+) exchange was performed on Li5La3Nb2O12 using CH3COOH. After X-ray powder diffraction experiments to check the quality of Li5-xHxLa3Nb2O12, the chemical formulation was determined by thermogravimetric analysis coupled with mass spectrometry and flame photometry. The results showed unambiguously that the Li(+)/H(+) exchange was not total and that some CH3COOH remained in the sample.

Structural characterization of a new acentric Ruddlesden-Popper layered perovskite compound: LiHSrTa2O7.

A new n = 2 member acentric Ruddlesden-Popper layered perovskite LiHSrTa(2)O(7) (LiDSrTa(2)O(7)) has been synthesized and structurally characterized from Rietveld treatment of its powder X-ray and high-resolution neutron diffraction data. It can be synthesized by a partial Li(+)/H(+) exchange from the mother phase Li(2)SrTa(2)O(7) either in solid state by NH(4)Cl or in dilute HNO(3) by controlling the amount of H(+). This compound crystallizes in the orthorhombic acentric space group Ama2 (no.

Mechanism of a reversible CO2 capture monitored by the layered perovskite Li2SrTa2O7.

We demonstrate for the first time, a new CO(2) capture ability monitored by a Ruddelsden-Popper compound. Under a humid CO(2) atmosphere, Li(2)SrTa(2)O(7) is transformed into LiHSrTa(2)O(7) releasing lithium hydroxide which combined with the atmospheric CO(2) leads to Li(2)CO(3). The presence of carbonate is confirmed by IR, thermal analysis coupled with mass spectroscopy and diffraction experiments (X-ray and neutron).

Ca(2+)/vacancies and O2-/F- ordering in new oxyfluoride pyrochlores Li(2x)Ca1.5-x square 0.5-xM2O6F (M = Nb,Ta) for 0 < or = x < or = 0.5.

New oxyfluorides Li(2x)Ca(1.5-x) square (0.5-x)M2O6F (M = Nb, Ta), belonging to the cubic pyrochlore structural type (Z = 8, a approximately 10.