Characterization and transport properties of semiconducting Fe2O3-Bi2O3-Na2B4O7 glasses

Semiconducting oxide glasses of the system Fe2O3-Bi2O3-Na2B4O7 were prepared by a press-quenching method. Their DC conductivity was measured in the temperature range of 300-473 K. In this temperature range, the DC conductivity increased from 10(-9) to 10(-5) Scm(-1) with increasing Fe2O3 concentration. Bi2O3 acted as a reducing agent for redox reaction during glass synthesis and affected the conductivity. Mossbauer results revealed that the relative fraction of Fe2+ increases with an increasing Fe2O3 concentration. The conduction mechanism was found to obey the non-adiabatic small polaron hopping model, and was mainly due to hopping between Fe-ions in the glasses. The small polaron coupling p was calculated and found to be in the range of 17.06-26.25. For varying glass compositions, hopping mobility and carrier density were calculated and their values were in the range of 3.66 x 10(-8)-8.17 x 10(-5) cm V-2(-1) s(-1) and 1.29 x 10(17)-5.04 x 10(18) cm(-3) at 400 K, respectively. (c) 2005 Elsevier B.V. All rights reserved.