Vibrational study of metal-substituted MPS3 layered compounds: MII1−xMI2xPS3 with MII = Mn, Cd, and MI = Cu (x = 0.13) or Ag (x = 0.50): II. Low-frequency Raman study and ionic transport

Abstract The low-frequency Raman spectra of Mn 0.87 Cu 0.26 PS 3 , Cd 0.87 Cu 0.26 PS 3 , Mn 0.5 Ag 1.0 PS 3 , and Cd 0.5 Ag 1.0 PS 3 layered compounds have been recorded from powder samples and/or single crystals between 15 and 800 K. The temperature dependences of these spectra reflect the dynamics of the M I ions and they have been fitted using different theoretical models. In Mn 0.87 Cu 0.26 PS 3 a nonlinear coupling between the Cu I translational mode perpendicular to the layer plane and an intralayer vibration governs the passage of the copper ions into the interlayer space, which is a determining step in the ionic conductivity process. Similar conductivity properties are expected in Cd 0.87 Cu 0.26 PS 3 . In contrast, this step is not observed in the silver-containing compounds.