Phase equilibria in the Ge-Bi-Te ternary system at 570-770 K temperature range

Two isothermal sections of the Ge-Bi-Te ternary system at 570 and 770 K have been constructed using metallography and X-ray diffraction data. Two non-stoichiometric Ge2-xBi2+xTe5 (D) and Ge4-xBi2+xTe7 (F) phases have been found at 770 K in addition to the known Ge3Bi2Te6 (A), GeBi2Te4 (B) and GeBi4Te7 (C) compounds. The Ge2-xBi2+xTe5 and Ge4-xBi2+xTe7 phases are characterized by nine- and 39-layer structures respectively. The isothermal section at 570 K has been constructed taking into account the formation of high members of the (GeTe)(n)Bi2Te3 (n = 1 to 9) and (Bi2Te3)(m)GeTe (m = 1 to 4) homologous series and ordered intermediate phases in the Bi-Te binary system.