Publications by authors named "Cyrille Galven"

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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).

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