Anomalous behaviors of elastic moduli, DC conductivity and optical properties in mixed transition–metal–ion (20-x)MnO₂–xFe₂O₃–80TeO₂ tellurite glass system

摘要

Mixed transition– metal–ion xFe 2 O 3 –(20-x)MnO 2 – 80TeO 2 glasses were prepared using melt-quenching method to study the D C conductivity, elastic and optical properties of the glasses.DC cond uctivity showed a strong increase for x ≤ 10 mol% Fe 2 O 3 before reaching a saddle-like behavior between 10 mol % ≤ x ≤ 15 mol%, followed by a large increase for x> 15 mol%. Longitudinal and shear velocities .? L and .? s exhibited non-linear behaviors and where bothincreased for x ≤ 10 mol% with an anomalous drop at x = 15 mol% Fe 2 O 3 ,followed by a large increase at x> 15 mol%. Independent longitudinal modulus (C L ), shear modulus (μ) and bulk modulus (K e ) showed similar behaviors to both velocities. Hardness (H), Debye temperature (θ D ) and glass transition temperature (T g ) also substantially increased for x ≤10 mol% before reaching a saddle-like behaviorbetween 10 and 15 mol% Fe 2 O 3 . Subsequently, a slight increase at x>15 mol% was observed. The ano malous region between 10 mol% ≤ x ≤ 15 mol%coincided with DC conductivity saddle-like region and is suggested to be related to the mixed transition– ion effect (MTE).Meanwhile, in same region, optical band gap (E opt ) exhibited a maxima, whereas refractive index sho wed a minima, thereby indicating a variation in polarizability due to the changes in concentration of bridging and non-bridging o xygens.