Chemical reactions on the Bi 2Te 3–Bi 2Se 3 section in the process of crystal growth

Abstract

By methods of differential-thermal analysis and X-ray-phase analysis it is proved that the Bi 2Te 3–Bi 2Se 3 section is a system with a continuous series of solid solutions, with the formation of Bi 2Te 2Se compound below the solidus line. The formation of this compound has been confirmed both in experiment and by thermodynamic analysis (TDA). It has been found that after zone melting the temperature values of the liquidus and solidus lines correlate with those obtained for equilibrium systems and mentioned in the literature. The boundary has been identified for the existence of Bi 2Te 3− x Se x solid solutions, which lies at ∼14 mol% Bi 2Se 3 (Bi 2Te 2.58Se 0.42). TDA shows chemical interactions (reactions) resulting in the formation of Bi 2Te 2Se. It has been found that in the two-phase zone, the Seebeck coefficient values dramatically change in a jumping manner, with the points of extremum located on the boundaries of the two-phase zone. In the zone of Bi 2Te 2Se compound occurrence (33.3 mol% Bi 2Se 3), the values of the Seebeck coefficient and power factor are minimal.