On the Structural Phase Transition in a Perovskite-Type Diaminopropanetetrachlorocuprate(II) NH3(CH2)3NH3CuCl4 Crystal

Chemical preparation, differential scanning calorimetry and thermal stability differential thermal gravimetry studies, positron annihilation lifetime investigations, optical observations as well as electric properties of the NH3(CH2)(3)NH3CuCl4 crystal are presented. On the basis of the differential scanning calorimetry response the structural phase transition of the first order was observed at 436 K. The enthalpy and entropy of the phase transition are equal to 1120 J/mol and 2.57 J/(mol K), respectively. Differential thermal analysis and thermogravimetric analysis studies confirmed the phase transition at 436 K and one can conclude the chemical and thermal stability of the compound up to about 480 K. Optical observations showed a continuous change of colour from yellow to dark brown above the phase transition to 436 K. Dielectric measurements showed a significant increase of conductivity upon approaching the phase transition regions, with a significant increase above the phase transition temperature. An activation energy dependent on the temperature range, and different for each particular phase, is obtained from measurements of complex impedance.