engleski

Pressure-induced tuning of phase transition and role of disorder in electrical transport properties of
-SrxV6O15

We report the resistivity and thermoelectric power of
-SrxV6O15, for various stoichiometries, 0.6x1, and under pressures up to 1.7 GPa. The pristine system
x=1 exhibits a semiconductor-insulator transition at 155 K, which is evidenced in both resistivity and thermopower and is probably induced by charge ordering.We observe a pronounced change in the nature of the phase transition under pressure and we attribute it to the tuning of the nearest neighbor Coulomb interaction V. At ambient pressure, as the system moves away from stoichiometry to x1, disorder is introduced into the strontium sublattice and the phase transition is immediately suppressed. The temperature dependence of the thermoelectric power gradually weakens as the system moves away from x=1, indicating the importance of disorder. While for x1 compound thermoelectric power shows evidence of a localized contribution to the conduction, which may involve polaronic effects, the activation energies speak against small polarons in the pristine x=1 compound. We explain our results in a model of conduction through localized states in the off-stoichiometric systems and of thermally activated conduction in the pristine system.

PACS number
s: 71.30.h; 72.15.Eb

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