Phase Equilibria in the TlInSe2–TlInP2Se6– Tl4P2Se6 Quasiternary System

Abstract

For the first time the phase equilibrium of the Tl4P2Se6–TlInP2Se6 binary and TlInSe2–TlInP2Se6–Tl4P2Se6 ternary systems were investigated by the methods of physical-chemical analysis (DTA, XRD, MSA) and mathematical design in multi-component system. It has been established that the Tl4P2Se6–TlInP2Se6 system belongs to the eutectic type and characterized by the formation of boundary solid solutions on the basis of complex compounds. The space phase diagrams, projection of liquidus surface of the TlInSe2–TlInP2Se6– Tl4P2Se6 system were constructed. Ternary system characterized by two invariant processes – eutectic (L  mtmTl4P2Se6 + TlInSe2 + htmTlInP2Se6,705K) and peritectic (L + hhtmTl4P2Se6 TlInSe2 + htmTlInP2Se6,739K). On the basis of complex selenophosphate compounds takes place metatectic, eutectoid (Tl4P2Se6) and two peritectoid (TlInP2Se6) processes, respectively. Specifics of crystal structure of complex compounds were given from the position of the second coordination surrounded of atoms in cationic and anionic sublattice