Subsolidus binary phase diagram of (n-CnH2n+1NH3)2ZnCl4 (n = 14, 16, 18)

The thermotropic phase solid–solid transitions compound ( n -C n H 2 n +1 NH 3 ) 2 ZnCl 4 ( n = 14, 16, 18) were studied, and a series of their mixtures were prepared. These laminar materials contain bilayers sandwiched between metal halide layers. The low temperature crystal structures of the pure salts are characteristic of the piling of sandwiches in which a two-dimensional macro-anion ZnCl 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 14 H 29 NH 3 ) 2 ZnCl 4 -( n -C 18 H 37 NH 3 ) 2 ZnCl 4 and ( n -C 16 H 33 NH 3 ) 2 ZnCl 4 -( n -C 18 H 37 NH 3 ) 2 ZnCl 4 were established by differential thermal analysis and X-ray diffraction. 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.