DC Hopping conduction in Fe2O3–MgO–TeO2 glasses

Semiconducting oxide glasses in the Fe2O3–MgO–TeO2 system are fabricated by a press-quenching of glass melts using Fe2O3, Mg, and TeO2 raw materials and the dc conduction is investigated. The glass formation region represented by batch composition is determined as follows: Fe2O3=0–20; Mg=0–40; and TeO2=55–100 mol%. The glasses are n-type semiconducting. The dc conductivity gives 1.1×10−5 to 1.3×10−4 S cm−1 at 548 K for different glass compositions. The conductivity increases with increasing Fe2O3 and Mg contents. A redox model in the glass melt is proposed, which makes possible to explain the fraction of reduced transition metal ion C for different compositions. The conduction is attributed to non-adiabatic hopping of small polarons. The small polaron coupling constant γp is evaluated to be 21–33. For varying glass compositions hopping mobility and carrier density are estimated to be (1.1–5.8)×10−6 cm2 V−1 s−1 and 4.8×1019–1.5×1020 cm−3 at 548 K, respectively.