THE STRUCTURE AND DIELECTRIC-PROPERTIES OF THIN PZT-TYPE FERROELECTRIC-FILMS WITH A DIFFUSE PHASE-TRANSITION

By means of r.f. sputtering of the ceramic targets or pressed powder t argets with the chemical constitution of Pb (Zr0.52Ti0.46W0.01Cd0.01) O-3 the polycrystalline thin ferroelectric films with the perovskite t ype structure and of thickness d(f) = (1-2, 5) x 10(-6) m on metal (st ainless steel, platinum) or ceramic (polycor) substrates have been obt ained. In case of thin film deposition on steel substrate and on plati num at low temperatures (T-s < 723 K) the nonferroelectric intermediat e layer with the same chemical constitution but with the pyrochlore ty pe structure have been created. Results of the X-ray analysis and diel ectric investigations (low frequency dispersion) have proved existence of such a structure. The structural phase transition (P4mm reversible arrow Pm3m) takes place in the thin ferroelectric films. This is a di ffuse type transition and the degree of diffuseness depends on the str uctural perfection of the thin films. The measure of the structural pe rfection of the thin films was taken to be the mean value of the latti ce strains (microdeformations) (Delta d/d) where ''d''-interplane dist ance and the mean dimension (D) of the areas of coherent X-rays scatte ring ( crystallites). With increase in (Delta d/d) and decrease in D t he degree of diffuseness increases. For quantitative and qualitative d escribing of this dependence in thin PZT films the phenomenological mo del of diffused phase transition developed earlier by the authors for thin BaTiO3 films has been applied. In this case a good agreement betw een theory and experiment have been achieved for low values of (Delta d/d).