A new apparatus for total scattering measurements has been developed with a variable camera length using a 16-inch two-dimensional flat-panel detector to observe structural changes in amorphous and disordered crystalline materials substantially in real time on beamlines BL08W and BL04B2 at SPring-8. This paper presents the successful time-resolved pair distribution function analysis at SPring-8, and a newly developed program for data conversion from two-dimensional images into one-dimensional total scattering patterns.
Preparation of sulfide-based Li-ion conductive solid electrolytes by a liquid-phase process has been proposed as an effective route for industrial scaling-up. However, reaction mechanisms in the liquid-phase synthesis or the role of solvents in the reactions are not yet well understood. Here, the reaction between Li2S and P2S5 in the composition of 50:50 mol% mediated by a polar aprotic solvent (acetonitrile) was investigated. The study of the crystal and local structure of the 50Li2S:50P2S5 sample revealed large chemical changes upon crystallization, highlighting the initial formation of a polymer-like (PS3 − )n intermediate. In the base of the (PS3 − )n intermediate, the reaction pathways for the formation of the P2S6 2− , PS4 3− , and P2S7 4− anions are elucidated. These findings give a deeper insight into the reaction mechanisms governing the liquid-phase synthesis of sulfide solid electrolytes and provide more specific criteria by which to design novel materials with superior characteristics through this liquid-phase approach.
Reversible coloration−decoloration of tungsten phosphate glasses was observed by heat treatments at
temperatures between 300 and 500 °C which were far below the T
g (570 °C) under the ambient with
controlled partial pressure of hydrogen and/or water. The color center responsible for the coloration was
found to be an electron-trapped W5+. The assignment was done by detecting an anisotropic ESR singlet
of g = 1.7 and broad optical absorption bands extending from the visible to the near-infrared region. The
charge compensator of W5+ was found to be H+. Mechanisms of the coloration by heat treatments under
an ambient with the hydrogen-bearing species were proposed to be (1) decomposition of molecular water
or hydrogen at the surface of the glasses, (2) selective dissolution of the generated hydrogen atom by the
reaction with W6+ ions to form the W5+/H+ redox pair in the glasses, and (3) diffusion of the charge-compensating H+ into the glass. The decoloration process was expressed by the reverse reactions. The
rate of the coloration−decoloration was found to be determined by the diffusion of the atomic hydrogen.
The diffusion constant of the atomic hydrogen at 500 °C in the glass was found to be as large as 1.5 ×
10-6 cm2/s.
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