A CRITICAL-EXAMINATION OF MODELS FOR THE INTERPRETATION OF DIELECTRICLOSS MEASUREMENTS IN PHOTOGRAPHY

The measurement of dielectric loss in photographic emulsions is the on ly known method to determine the ionic conductivity of silver halide m icrocrystals contact-free and in situ. The frequency corresponding to the maximum of the dielectric loss curve is proportional to the ionic conductivity of the system. The standard models of Wagner/Sillars pred ict a single frequency maximum in the dielectric loss signals of two-p hase systems. Evidently this approach is not applicable to systems lik e octahedral and core-shell emulsions, which exhibit double loss peaks . The Pauly/Schwan theory, which is based on a three-phase model, shou ld in principle provide an explanation for loss signals of this kind. In this study, we revised and expanded the Pauly/Schwan theory and tes ted the congruence of model calculations with physical reality by a se ries of experiments on monodisperse cubic and octahedral AgBr emulsion s with different spectral sensitizers and stabilizers as addenda. The result of this examination is that within the framework of the Pauly/S chwan formalism it is not possible to describe the observed dielectric loss signals of photographic emulsions satisfactorily.