TRANSPORT-PROPERTIES OF SEMICONDUCTING GLASS-CERAMICS IN THE SYSTEM BAO-FE2O3-B2O3-SB2O3, BAO-FE2O3-B2O3-AS2O3

DC resistivities of glass-ceramics in the system BaO-Fe2O3-B2O3-X2O3 (X=Sb, As) containing alpha -Fe2O3 crystalline phase have been investigated over the temperature range 85-350 K. The specimens exhibit fairly high room-temperature conductivities of the order of 10-4 Omega -1 cm-1. The resistivity variation as a function of temperature is explained on the basis of a small polaron hopping conduction mechanism between the iron ion sites of different valence states in the glass phase. Mott's low-temperature T-1/4 law and the recently formulated Triberis and Friedman high-temperature T-1/4 variation are found to be obeyed by the present glass system. The density of localised states in the system calculated using the above models is found to be of the order of 1020 eV-1 cm-3. However, the T-2/5 law of Triberis and Friedman gives a value for the density of localised states which is consistent with the TM ion concentration within the glass phases of the glass-ceramic system. © 1990 IOP Publishing Ltd.