Electrical relaxation in iron-containing glasses

Glasses with composition 70 mol%(SiO/sub 2/, B/sub 2/O/sub 3/, P/sub 2/O/sub 5/, TeO/sub 2/)-15 mol% Fe/sub 2/O/sub 3/-15 mol%(BaO, CaO) were prepared by the conventional melt quenching technique. The electrical relaxation of these glasses has been studied in the frequency range 20 to 10/sup 5/ Hz. The small polaron hopping between iron ions in a different valence state Fe/sup 2+/ to Fe/sup 3+/ is found to be the principal conduction mechanism. The ratio of Fe/sup 2+/ ions to the total iron content, C=Fe/sup 2+//Fe/sub tot/, is one of the factors determining the electrical conductivity. The glass former has a minor influence on dc conductivity, except of TeO/sub 2/ glass where conductivity is three order of magnitude higher than those of other glasses. The ac conductivity as a function frequency is divided into two domains, a dc plateau, followed by a power law in frequency. These two regions are well distinguished in the complex plot of electric modulus where all data points for different temperatures reside on the single plot. The results are discussed in the frame of the Hunt theory of dielectric relaxation in glasses containing mobile charge carriers.