Millimeter wave spectroscopy and color centers of MAg4I5 (M=Rb, K and NH4) family
Abstract Reflectivity spectra of superionic conductors of MAg4I5 (M=Rb, K and NH4) and Rb4Cu16Cl13I7 were measured in a spectral region between 3.5 and 200 cm−1 at a temperature range from 15 K to 470 K. A structure of “ionic plasmon” was observed near 10 cm−1 (MAg4I5) or 20 cm−1 (Rb4Cu16Cl13I7) in energy loss function spectra. Coloration of MAg4I5 by X-ray irradiation was observed. The absorption band were intense in NH4Ag4I5 only by hole centers. The coloration rate of NH4Ag4I5 increases drastically at the temperature around the superionic phase transition as observed in RbAg4I5 and KAg4I5.