Subsolidus phase diagram of binary system of thermotropic phase transitions compounds ( n-C nH 2 n+1 NH 3) 2MnCl 4 ( n = 12, 14, 16)

Abstract

The thermotropic phase transitions in the perovskite type layer compound ( n-C n H 2 n+1 NH 3) 2 MnCl 4 ( n = 12, 14, 16) were studied and a series of their mixtures were prepared. The low temperature crystal structures of the pure salts are characteristic of the piling of sandwiches in which a two-dimensional macro-anion MnCl 4 2− is sandwiched between two alkylammonium layers. These layers become conformationally disordered in the high temperature phases. The subsolidus binary phase diagrams of ( n-C 12H 25NH 3) 2MnCl 4–( n-C 14H 29NH 3) 2MnCl 4 and ( n-C 14H 29NH 3) 2MnCl 4–( n-C 16H 33NH 3) 2MnCl 4 were established by differential thermal analysis (DTA) and X-ray diffraction (XRD). In each phase diagram, an intermediate compound and two eutectoid invariants were observed. There are three noticeable solid solution ranges ( α, β, γ) at the left boundary, right boundary and middle of the phase diagram.