Untersuchungen zum quasibinären System Bi₂Te₃/BiCl₃/Investigations on the Pseudobinary System Bi₂Te₃/BiCl₃

Abstract

The phase diagram of the pseudobinary sytem Bi 2 Te 3 /BiCl 3 was investigated by DTA, total pressure measurements, and X-ray phase analysis. Only BiTeCl exists as a ternary phase in this system. The compound melts incongruently at 430 °C. The heat of formation and the standard entropy of BiTeCl were calculated from vapor pressure data: ΔH° B (BiTeCl, f, 298) = (-39,5 ± 1,6) kcal/mol; S° (BiTeCl, f, 298) = (34,4 ± 2,7) cal/K· mol. The heat of formation of BiCl 3 was determined on the basis of the heat of solution of BiCl 3 and Bi 2 O 3 , and the heat of formation of Bi 2 O 3 : ΔH° B (BiCl 3 , f, 298) = (-95,9 ± 0,9) kcal/mol.