Synthesis and electrical properties of Fe2O3-MoO3-TeO2 glasses

Semiconducting glasses of the Fe2O3-MoO3-TeO2 system were prepared by the press-quenching method and their d.c. conductivities in the temperature range 373-573 K were measured. The glass formation region was found to be Fe2O3=0-20 mol.%, MoO3=0-40 mol.%, TeO2=50-100 mol.%. The Seebeck coefficients showed these glasses to be n-type semiconductors. The glasses had conductivities sigma ranging from 10(-8) to 10(-4) S cm(-1) at temperatures from 373 to 573 K. The d.c. conductivity increased with increasing Fe2O3 content or MoO3/TeO2 at fixed amount of Fe2O3. Because of its slight effect on the conductivity. MoO3 was considered to act as a reducing agent for redox reaction during glass synthesis. Electrical conduction of the glasses was confirmed to be due to nonadiabatic small polaron hopping, and the conductivity was primarily determined by hopping carrier mobility. The polaron band width, J, ranged from 0.09 to 0.18 eV depending on the Fe-Fe spacing. (C) 1997 Elsevier Science S.A.