Electrical and Magnetic Properties of Molten Tlx(AgTlSe2)1 ‐ x Alloys

Abstract

AbstractThe electrical conductivity, the magnetic susceptibility, and the thermoelectric power of liquid Tl‐AgTlSe2 alloys have been obtained, respectively, as a function of temperature and composition from near the liquidus temperature up to about 900°C. In the region of low Tl concentration, the temperature dependences of these electronic properties follow an Arrhenius‐type activation process where the carriers excite thermally into the extended states. In the Tl rich region, above 66.7 mol‐% Tl, the temperature dependence of the conductivity becomes extremely small at high temperature, suggesting that the metallic contribution is important in this range. The electrical conductivity shows a deep minimum around 66.7 mol‐% Tl, the value of which was measured as 4.0 Ω−1 cm−1 at 400°C. Corresponding to this behaviour, a steep diamagnetic maximum was observed in the susceptibility vs. composition curve. Furthermore, the thermoelectric power changes its sign around this composition from positive in the AgTlSe2 excess side to negative in the Tl excess side. The maximum positive value of the thermoelectric power in the vicinity of 66.7 mol‐% Tl was roughly 290 μV · deg−1 at 600°C. The asymmetric form of isotherms for these quantities around 66.7 mol‐% Tl resembles that in the related liquid Tl – Se alloys which have been examined in detail with respect to their electronic behaviour indicating that the metal‐semiconductor transition occurs at the composition corresponding to AgTl3Se2 (66.7 mol‐% Tl) in the liquid system Tl‐AgTlSe2.