Variable-range-hopping conduction via indium impurity states in Pb0.78Sn0.22Te solid solution

The Seebeck coefficient S was measured in a wide temperature range T < 100 K in Pb0.78Sn0.22Te solid solutions doped with 3 at. % of In, with additional Cl doping of up to 3 at. %. The temperature derivative partial derivative\S\/partial derivative T changes its sign from negative to positive below 100 K. Theoretical estimations in terms of hopping conduction via highly localized indium-related states show that the transition to variable-range-hopping conduction must occur at temperatures of about 50-100 K, in agreement with the obtained experimental data. (C) 2000 MAIK "Nauka/Interperiodica".