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Density, DC conductivity and "B wide-line NMR investigations have been carried out for xFez03<50x)PbO-508203 glasses (0 < x 4 20 mol%). The NMR specha indicated the formation of non-bridging oxygen ions in the borate nehvork upon introducing Fe&. The DC conductivity and the activation energy for conduction change markedly with Fe203 content. The high-temperature conductivities can be described by Man's model for the phonon-assisted hopping of small polarons. The polaron happing is shown to be non-adiabatic. The lowtemperahut conductivities are characterized by the variable-range hopping mechanism. For Fez03 contents greater than 15 mol%, glasscrystal composites are formed, changing greatly the electrical properties, and other conduction mechanism is to be assumed. * Dedicated to Professor Dr W Miiller-Warmuth (Miinster, Germany) on the occasion of his 65th birthday.

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Glasses of the formula xPbCl2-(30-x)PbO-40B2O3-30P2O5 (0