Transport properties of polycrystalline Tl0.33MoO3 compounds.

Abstract

Transport coefficient measurements (electrical conductivity, thermoelectric power, and Hall coefficient) have been performed on a compact ${\mathrm{Tl}}_{0.33}$${\mathrm{MoO}}_{3}$ polycrystalline compound in a wide temperature range (200\char21{}400 K). Experimental results are interpreted with the help of a p-type semiconductor model with two inverted deep levels near the midgap. The valence band and the conduction band are assumed to be formed from the ${d}_{\mathrm{xy}}$ orbitals of molybdenum atoms in the ${\mathrm{Mo}}_{6}$${\mathrm{O}}_{22}$ cluster leading to narrow \ensuremath{\pi}-bonding bands. The donor and acceptor levels may be formed from nonbonding ${d}_{\mathrm{xy}}$ orbitals arising, respectively, from anionic and ${\mathrm{Tl}}^{+}$ defects. Electron paramagnetic resonance and magnetic measurements are in good agreement with the theoretical band semiconductor model which has been retained.