Phase transition in the bidimensional compound [C6H5(CH2)(2)NH3](2)CdCl4

Bis phenyl 2 ethylammonium lead tetrachloride ([C6H5(CH2)(2)NH3](2)CdCl4) i s a new member of the family of perovskite-type layer compounds. It exhibit s a structural phase transition Phase I (379 K) --> Phase II. This transition is characterised by DSC measurements, X-ray diffraction, di electric measurements and Raman scattering on polycrystalline samples. The space groups and the cell parameters of phases I and II were determined by X-ray diffraction on single crystals and powder samples. The phases I and I I have the same space group Pcab with Z = 4. The transition is also of firs t order and involves both organic action motions and CdCI6 octahedral defor mations. This transitional behaviour and the crystal dynamics will be discu ssed and compared with those found in the literature for homologous compoun ds.