The phase transition tuning by the Fe(III)/Co(III) substitution in switchable cyano-bridged perovskites: (C3N2H2)2[KFexCo1-x(CN)6]
The single-crystals of the mixed [C3H5N2]2[KFexCo1-x(CN)6] crystals, with different ratio of x = 0, 0.29, 0.42, 0.51, 0.63, 0.70, 0.85, 1, have been grown from aqueous solutions. The thermal stability of the crystals has been determined using both DTA and TGA analysis. DSC has revealed sequences of structural phase transitions (PTs). We have found four solid phases for crystals with the concentrations x < 0.6 and three phases - above this concentration. The Fe(III) concentration was estimated using SEM technique. We have found the linear relationship of Tc versus molar concentration of Fe(III) for the IVIII PT. Based on the obtained results, the phase diagram has been constructed. The mechanism of the structural PTs has been discussed based on the results of the dielectric relaxation, NIR – IR and Raman spectroscopy and X-ray measurement. The dielectric switching has been observed for all the analysed mixed-crystals. All the crystals exhibit ferroelastic properties.