Cu₆РS₅Br superionic conductors are characterized by high ionic conductivity and intrinsic structural disoder caused by the presence of vacancies in copper cation sublattice. Cu₆РS₅Br single crystals were grown by chemical transport reactions. Micro- and nanopowders with average grain size down to 15 nm were obtained by ball milling. The average grain size was estimated from the X-ray diffraction data. Cu₆РS₅Br nanopowder-based composites were obtained by embedding them in polymer films of polytrifluorethylene, polyvinyl chloride, and a copolymer of styrene and maleic anhydride. Raman spectra of the micro- and nanopowders as well as the Cu₆РS₅Br-based nanocomposites were measured at room temperature in a 90^o geometry using a double grating LOMO DFS-24 monochromator and a He-Ne laser (632.8 nm).

In comparison with the single crystals, in Cu₆РS₅Br micro- and nanopowders and in the composites on their base an essential increase of Rayleigh scattering is observed, masking the lower-frequency bands below 100 cm^-1. Therefore, in the Raman spectra two well separated bands are observed, the lower-frequency one being a superposition of the Е and F₂ symmetry bands, the higher-frequency one corresponding to the A₁ symmetry mode. The crystallite size decrease results in a shift towards lower frequencies, broadening and decrease of intensity for both bands. The changes observed with the crystallite size decrease are explained by Frohlich surface modes revealed in the Raman spectra.

Contrary to the nanopowders spectra, in the Raman spectra of nanocomposites only the A₁ band is distinctly observed while the one due to the superimposement of the Е and F₂ symmetry modes is extremely weak what is probably related to the insufficient concentration of the Cu₆PS₅Br nanocrystallites in the matrix. Besides, no changes in the Ramans spectra of the composites, dependent of the matrix type, are observed.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/15660 must be provided.

1. Raman scattering studies of disordering processes in Cu₆P(S_1-xSe_x)₅Br_1-yI_y superionic conductors