Structural phase transitions in the kagome lattice based materials Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5)

The solid solution Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5) has been investigated crystallographically between 100 and 300 K using synchrotron X-ray powder diffraction and, in the case of x = 0, neutron powder diffraction.Comment: 14 pages, 9 figure

The nature of anionic clusters in anion excess fluorite-type oxidefluoride solid solutions in MF-BiF3-BiOF systems (M = Na, K)

Various compositions of the range of fluorite-type oxidefluoride solid solution in the NaF-BiF3-BiOF system are investigated by 19F NMR spectroscopy. Using the following formulation, Na0.5(1−z−h)Bi0.5(1+z+h)F2+z−hOh, this study is undertaken as a function of the anion excess (z) and the oxygen content (h). It results in the existence of two fluoride sublattices in the solid solution range. An approach to the nature of the fluorine-oxygen order is proposed when the compositions become richer and richer in BiOF. The clustering model is then extended to the homologous potassium oxidefluoride solid solutions

Structural phase transitions in the kagome lattice based materials Cs_2-xRb_xSnCu₃F₁₂ (x = 0, 0.5, 1.0, 1.5)

The solid solution Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5) has been investigated crystallographically between 100 and 300 K using synchrotron X-ray powder diffraction and, in the case of x = 0, neutron powder diffraction. For Cs2SnCu3F12 (x = 0), there is a structural transition from the previously reported room temperature rhombohedral symmetry (R[3 with combining macron]m) to monoclinic (P21/n) symmetry at 170 K. This transformation is repeated for the x = 0.5 composition, but with an increased transition temperature of 250 K. For x = 1.0 the monoclinic phase is found at 300 K, suggesting that the transition temperature is increased even further. For x = 1.5 a different behaviour, more akin to that previously reported forCs2SnCu3F12, is found: a single phase transition between rhombohedral symmetry (R[3 with combining macron]) and triclinic symmetry (P[1 with combining macron]) is found at 280 K. In agreement with previous single crystal studies, Cs2SnCu3F12 powder exhibits strong antiferromagnetic interactions (Θ ~ −268 K) and long-range magnetic order at TN ~ 19.3 K. The finite magnetic moment observed for T &lt; TN might be explained by a Dzyaloshinskii–Moriya interaction, due to the lowering of symmetry from rhombohedral to monoclinic, which was not suggested in the earlier single crystal study.</p

Effect of oxygen on short-range order in the Ba1-xBixF2+x solid solution

Various compositions within the range of the fluorite-type solid solution in the BaF2–BiF3–BiOl.5 system are investigated by impedance spectroscopy. This study is carried out along two lines of compositions: δ1, corresponding to the Bal−2z/3Bi2z/3F2+4z/3Oz solid solution, where z is the oxygen rate; and δ2, corresponding to the Bal−xBixF2+x−0.30O0.15 solid solution, where x is the bismuth rate. An approach to the nature of the fluorine–oxygen order is proposed which derives from the clustering process in the Bal−xBixF2+x fluoride solid solution

Fluorite-like phases in the BaF 2 -BiF 3 -Bi 2 O 3 system-synthesis, conductivity and defect clustering

Abstract A fluorite-like solid solution Ba 1 À x Bi x O z F 2 + x À 2z on the basis of cubic BaF 2 was synthesised in the BaF 2 -Bi 2 O 3 -BiF 3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Å , c = 18.151(1) Å .

New anion-conducting solid solutions Bi_1−<i>x</i>Te_<i>x</i>(O,F)_2+<i>δ</i> (<i>x</i> > 0.5) and glass-ceramic material on their base

The anion-excess fluorite-like solid solutions with general composition Bi1−xTex(O,F)2+δ (x > 0.5) have been synthesized by a solid state reaction of TeO2, BiF3 and Bi2O3 at 873 K with following quenching. The homogeneity areas and polymorphism of the I ↔ IV Bi1−xTex(O,F)2+δ phases were investigated. The crystal structure of the low temperature IV-Bi1−xTex(O,F)2+δ phase has been solved using electron diffraction and X-ray powder diffraction (a = 11.53051(9) Å, S.G. Ia-3, RI = 0.046, RP = 0.041). Glass formation area in the Bi2O3-BiF3-TeO2 (10% TiO2) system was investigated. IVBi1−xTex(O,F)2+δ phase starts to crystallize at short-time (0.5-3 h) annealing of oxyfluoride glasses at temperatures above Tg (600-615 K). The ionic conductivity of the crystalline Bi1−xTex(O,F)2+δ phase and corresponding glass-ceramics was investigated. Activation energy of conductivity Ea = 0.41(2) eV for the IV-Bi1−xTex(O,F)2+δ crystalline samples and Ea = 0.73 eV for the glass-ceramic samples were obtained. Investigation of the oxyfluoride samples with a constant cation ratio demonstrates essential influence of excess fluorine anions on the ionic conductivity

Fluorite-like phases in the BaF2-BiF3-Bi2O3 system-synthesis, conductivity and defect clustering

A fluorite-like solid solution Ba1 − xBixOzF2 + x − 2z on the basis of cubic BaF2 was synthesised in the BaF2-Bi2O3-BiF3 system and the homogeneity range at 873 K was determined. The samples were studied by X-ray powder diffraction and electron diffraction, and their transport properties were measured by the complex impedance method at 300-623 K. Tendencies of variation of lattice parameters and transport properties were determined. These tendencies are discussed on the basis of a defect clustering hypothesis. Thermal treatment at 573 K of the solid solution, quenched from 873 K results in the formation of a new ordered tetragonal fluorite-like phase with lattice parameters a = 9.5355(4) Å, c = 18.151(1) Å