Electrical Conductivity and Superconductivity in the γ Phase of the Tl–Te System

Abstract

Two methods for the preparation of single crystals of the γ phase of the Tl–Te system, Tl₅Te₃, are described. An analysis of electrical resistivity data on both single‐crystal and polycrystalline material over the temperature range 4.2° to 500°K and thermal conductivity data on polycrystalline material over the temperature range 77° to 360°K indicates metallic behavior. Typical electrical characteristics at 300°K are: resistivity 2.5×10⁻⁴Ω·cm, carrier concentration 1.5×10²²/cm³, and mobility 2.0cm²/V·sec. A transition to the superconducting state was observed at 2.19°K; this transition was studied as a function of magnetic field strength. The existence of superconductivity in the γ phase is generally compatible with predictions for the occurrence of superconductivity in degenerate semiconductors and semimetals with positive Hall coefficients.