ELECTRICAL-CONDUCTIVITY AND OPTICAL-ABSORPTION STUDIES IN SUPERIONIC RBAG4I5 THIN-FILMS

Electrical conductivity in thin films of the superionic conductor RbAg 4I5 was found to be in very good agreement with the best bulk value (0.27 Ω-1 cm-1). From the conductivity data, the activation energy for Ag+-ion conduction, and the free-ion-like parameters such as the mean free path and lifetime in the excited state have been deduced. The phase transition at 210 °K has also been observed, and the activation energy for conduction before and after the phase transition has been evaluated. Optical absorption studies in these films reveal a well-defined exciton state at 3750 Å at 300 °K. Also, a weak band is observed at 3350 Å on the higher-energy side of the exciton band which appears to be evidence for the existence of large-radius excitons. A broad band observed at 4850 Å has been attributed to the existence of silver colloids in the films. A forbidden internal transition in the Ag+ ion has been observed at 4250 Å.