AN INFRARED SPECTROSCOPIC STUDY OF THE STRUCTURAL PHASE-TRANSITION IN THE PEROVSKITE-TYPE LAYER COMPOUND [N-C16H33NH3]2COCL4

The solid-solid phase transitions in the perovskite-type layer compound [n-C16H33NH3]2CoCl4 have been studied by infrared spectroscopy. The new phase transition at 340 K was found by the comparison of DSC results. A temperature dependence study of the i.r. spectra provides the evidence for the occurrence of a structural phase transition related to the dynamics of the alkylammonium ions and hydrogen bonds. The main transition at 374 K corresponds to the conformational order-disorder change of the chain which probably couples with reorientational motions of the NH3 polar heads. The GTG or GTG' defects appear in the high temperature disordered phase.