The dc conductivity of MoO3-TeO2 glasses prepared by melt
quenching has been investigated in the temperature range 323-473 K. Seebeck
coefficient measurements indicate the glasses to be n-type. The conductivity
increases with increase of MoO3 content and at 418 K varies from about
6×10-6 to 1×10-8 S cm-1. The conduction is
attributed to non-adiabatic hopping of small polarons due to the different
valence states, Mo5+ and Mo6+, the existence of which was confirmed
from x-ray photoelectron spectroscopy analysis of the glasses. Fourier
transform infrared spectroscopic studies show the presence of MoO6,
MoO4, TeO3 and TeO4 structural units in the glasses.
Electrical and optical properties of MoO 3 -TeO 2 amorphous films prepared by vacuum deposition method were investigated. X-ray diffraction patterns show an amorphous structure. The dc conductivity of the films was measured in the temperature range 323-523 K and follows a non-adiabatic small polaron hopping conduction mechanism between Mo 4þ and Mo 5þ , confirmed by X-ray photoelectron spectroscopy measurements. Conductivity of the films increases with increase of MoO 3 content. The Seebeck coefficient indicates the films to be n-type semiconductor. Optical absorption edge analysis gave a band gap energy of 2.7-2.9 eV depending on composition. The Urbach tail analysis gave the width of localized states between 0.23 and 0.25 eV.
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