Correlation between the band-gap energy and the electrical conductivity in MPr2W2O10 tungstates (Where M = Cd, Co, Mn)

Abstract

The values of the direct allowed energy gap determined from the UV-vis-NIR measurements and Kubelka– Munk transformation decrease from 3.38 via 2.70 to 2.42 eV for MPr2W2O10 in the sequence M = Cd, Co, Mn, while the values of the activation energy increase from 0.11 via 0.44 to 0.47 eV in the same sequence. In other words, the higher the activation energy, the smaller the energy gap. Because the energy gap is typical for insulators, so electron transport phenomena are considered under the Poole–Frenkel effect and small-polaron mechanism.