DC conductivity of Fe2O3-Bi2O3-B2O3 glasses

Fe2O3-Bi2O3-B2O3 system of glasses were prepared by a press-quenching metho d from glass melts, and their de conductivities (sigma) were determined in the temperature range 373-573 K. The glass formation region was found to be : Fe2O3 = 0-40 mol%, Bi2O3 = 0-100 mol%, and B2O3 = 0-100 mol%. The negativ e values of Seebeck coefficient showed these glasses to be n-type semicondu ctors. For temperatures from 373 to 573 K, the de conductivity increased fr om 10(-8) to 10(-5) S cm(-1) with increasing Fe2O3 content. Bi2O3 acted as a reducing agent for redox reaction during glass synthesis and effected the conductivity. Different values of the activation energy for two-temperatur e regions were interpreted to be due to the formation of non-bridging oxyge n ion in the glass network, or the variation of dielectric constant probabl y owing to a phase separation. Electrical conduction of the glasses was con firmed to be non-adiabatic small polaron hopping. The conductivity was prim arily determined by carrier mobility. (C) 1999 Elsevier Science S.A. All ni ghts reserved.