Physical, optical and electrical studies of P2O5-TeO2-ZnO-V2O5-Fe2O3 glasses

We report on physical, mechanical, optical properties and dc conductivity of (P 2 O 5 ) 0.25 + (TeO 2 ) 0.15 + (ZnO) 0.1 + (V 2 O 5 ) 0.50-x + (Fe 2 O 3 ) x ; 0.05 < x < 0.30 glasses. The density is found increased monotonically from 3.2533 g/cm 3 to 3.6368 g/cm 3 and molar volume decreased from 55.151 to 47.810 cm 3 /mol indicating induced network modification due to dopant content. Making use of density and composition of the glasses in the Makishima-Mackenzie's model, various elastic moduli including hardness and fractal bond connectivity were evaluated and assessed. UV–Vis absorption spectra were measured for the wave length range 200 nm - 800 nm. Optical band gaps (E gap ), refractive index (n), molar refraction (R m ), reflection loss (R L ), molar polarizability (α m ), metallization criterion (M), dielectric constant (ε) and optical dielectric constant (ε 0 ) were evaluated. The obtained E gap in the range 2.481 eV–2.865 eV and n values in the range 2.899–4.108 indicated that these glasses are useful for optoelectronic applications. The dc conductivity (σ dc ) measured for the temperature range 300 K–525 K was found to vary as per Mott's small polaron hopping model at high temperature and Mott's variable range hopping model at lower temperatures. At high temperature, conductivity passed through a minimum of 1.19 × 10 −3 (Ωm) −1 and activation energy passed through a maximum of 0.532 eV for composition x = 0.2. This is identified to be due to mixed transition effect, MTE occuring at x = 0.2 and attributed to Anderson's localization of charges. Density of states was found to be in the range 10 21 –10 22 eV −1 cm −3 . For the first time, MTE has been observed in phospho-tellurite glasses.