Effect of annealing in an H2 gas atmosphere on the physical properties for 70V2O5·30TeO2 (mol%) glasses

Powdered 70V2O5·30TeO2 (mol%) glasses were annealed in an H2 gas atmosphere at 473 K for 1 h and 2 h, respectively. The difference between their physical properties before and after annealing was investigated. The mass of the powders decreased with an increase in the annealing time. Glass transition temperature (Tg) was 512 ± 0.1-513 ± 0.1 K for the annealed powders, indicating that the Tg values became lower than the as-quenched glass powder (Tg = 517 ± 0.1 K). The fraction of reduced vanadium ion (Cv = V4 + / (V4 + + V5 +)) increased with an increase in the annealing time: Cv = 0.020 ± 0.003, 0.024 ± 0.003 and 0.0272 ± 0.0033. From IR observation, it was determined that the glass structure in the annealed glasses ultimately incorporated a much larger amount of TeO3 trigonal pyramid units compared with the as-quenched glass powder. It was determined that the DC electrical conductivity (σ) of the pelletized powders, which were n-type semiconducting, depended on the annealing time of the powders. The largest σ was (5.78 ± 0.28) × 10− 5 S cm− 1 at 473 K for the pellet of the powder annealed for 2 h. The activation energy for electron hopping (W) was determined to be 0.380 ± 0.0005-0.420 eV ± 0.0005 eV, indicating that W decreased with an increase in the annealing time. The annealing contributed to the release of O from the glasses by changing the unit in the glasses from the TeO4 to TeO3: TeO4 + H2 → TeO3 + H2O ↑.