The problem of how to relate macroscopic conductivity relaxation measurements to the microscopic movements of ions was addressed. Upon analysing the results of a stochastic transport theory for charged carriers, it was found that the electric modulus gave the most suitable representation of the macroscopic data which described the microscopic movement of the ions. It was found that the electric modulus faithfully reproduced the shape of the dispersion of the microscopic ion movements; although the entire electric modulus relaxation time spectrum was shifted uniformly away from the microscopic ionic hopping relaxation time spectrum by a predictable frequency-independent factor. Nuclear spin relaxation constituted a microscopic probe of ion movements. A combined study of ionic motion, using electrical relaxation and nuclear spin relaxation methods in a crystalline ionic conductor, provided a means of checking the theoretical relationship between the macroscopic electric modulus spectrum and the microscopic ionic hopping relaxation spectrum. It was noted finally that recent advances in the understanding of experimental data had indicated the importance of ion-ion interactions in many ionically conducting crystals, glasses and melts.

Recent Advances in Relating Macroscopic Electrical Relaxation Data to Microscopic Movements of the Ions in Ionically Conducting Materials. K.L.Ngai, C.Leon: Solid State Ionics, 1999, 125[1-4], 81-90