Absorption spectra and excitons in solid electrolytes CsyRb1-yCu4Cl3I2 (y = 0.5; 1)

E.N.Kovalenko, V.K.Miloslavsky, O.N.Yunakova


Kharkiv State University, 4 Svobody Sq., 310077 Kharkiv, Ukraine

Received April 20, 1998

Electron absorption spectrum of the superionic conductor CsyRb1-yCu4Cl3I2 (y = 0.5; 1) has been studied. The observed narrow absorption bands in the 3.5-6 eV interval have been shown to be related to excitons localized in Cu(II)Hal and Cu(III)Hal sublattices of the above compounds. A larger forbidden gap as compared to Eg in CuI and CuCl is found to be defined by smaller number of Cu ions in the second coordination sphere of the compound crystal lattice. Some specific features associated with gamma beta and beta alpha phase transitions have been revealed in the temperature dependence of the spectral position and half-width of the low-frequency excitonic band. The temperature-related broadening of the excitonic band in the dielectric gamma-phase has been shown to be defined by exciton-phonon interaction and generation of Frenkel defects with low activation energy.

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