The thermotropic phase transitions in the perovskite type layer compound (n-CnH2n+1NH3)(2) MnCl4 (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 MnCl42- is sandwiched between two alkylammonium layers. These layers become conformationally disordered in the high temperature phases. The subsolidus binary phase diagrams of (n-C12H25NH3)(2)MnCl4-(n-C14H29NH3)(2)MnCl4 and (n-C14H29NH3)(2)MnCl4-(n-C16H33NH3)(2)MnCl4 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 (alpha, beta, gamma) at the left boundary, right boundary and middle of the phase diagram. (C) 2008 Elsevier B.V. All rights reserved.