Concept of Mismatch and Relaxation Derived From Conductivity Spectra of Solid Electrolytes

摘要

Crystalline ion conductors like RbAg_4I_5 and others display a characteristic shape of their discpersive conductivities at frequencies below the microwave regime. As the temperature is decreased, the onset ofthe dispersion is shifted to lower frequencies and thus the characteristic shape of the dispersion becomes visible in an increasingly broad frequency range. In a log-log plot of the frequnecy-dependent ocnductivity, the slope is found to increae continuously, but not to surpass unity. For the first time, this behaviour is now consistently explained. The particular shape of the dispersion is shown to be equivalent ot a proportionality fo the rates of relaxation via the single-and many-particle routes. This is the essence of the concept of mismatch and relaxation. Model conductivity spectra based on the CMR include the UDR as well as the NCL behavior. BOth universalities are thus traced back to a common dynamic origin.