The dependence of ionic transport properties on the structure and composition of perovskites Li0.5 - x Na x La0.5TiO3 (0 ≤ x ≤ 0.5) has been analyzed by means of ND, XRD, NMR, and impedance spectroscopy. Local lithium mobility is shown to decrease progressively by 2 orders of magnitude along the series; however, long-range dc conductivity decreases sharply at x = 0.2 more than 6 orders of magnitude. The decrease of dc conductivity from values typical of fast ionic conductors, 10-3 S/cm at room temperature, to values of insulators, 10-10 S/cm, is discussed in terms of a three-dimensional percolation model for lithium diffusion. As deduced from XRD and ND data, the number of vacant sites in conduction pathways is controlled by the amount of Na and La in the perovskite.

Investigations of impurity centers, electrical resistivity and microstructure of BaTiO 3 ceramics doped with rareearth ions Y, La, Nd, Sm, Dy and Lu at concentrations x~0.001±0.005 were carried out. Electron paramagnetic resonance, X-ray diffraction and electron microscopy were used for measurements. The most intense EPR lines were shown to belong to paramagnetic complexes Fe 3z ±V O and Ti 3z ±Ln 3z (Ln~rare-earth ion, V O~o xygen vacancy). A change in symmetry of the center Fe 3z ±V O at the transition temperature from the ferroelectric to paraelectric phase has been revealed for the ®rst time. Measurements of the dependence of EPR line intensities and electrical resistivity with rare-earth ion concentrations were performed. The observed correlation in their behaviour showed an essential role of the identi®ed paramagnetic complexes in the appearance of BaTiO 3 ceramic semiconducting properties and the positive temperature coef®cient of resistance (PTCR) effect. The latter effect was at a maximum for x#x c where x c #0.002±0.003 is the critical rare-earth ion concentration which determines the excess charge compensation mechanism. Up to x c , the rare earths investigated, (except for the small ion Lu), substitute for barium, and the main compensation mechanism is an electronic mechanism. At high concentrations (xwx c ) in the case of large ions (e.g. La), substitution is at barium sites, with the creation of titanium vacancies, whereas intermediate ions (e.g. Y) begin to substitute for titanium. The in¯uence of impurities on the BaTiO 3 microstructure, including the grain sizes, is discussed.

Ferroelectric PbTiO3 nanoparticles were synthesized to be used as inorganic components of new composite materials based on a liquid crystalline elastomer (LCE) matrix. The preparation and characterization of the composite materials, with a relatively high concentration of PbTiO3 nanoparticles, in the form of thin films is described. The composite films retain the thermomechanical response typical of standard LCEs and the nanoparticles are distributed in the film in anisotropic structures indicating the presence of a coupling between the LCE ordered matrix and the nanomaterials. The nematoelastic coupling and the supercritical nature of the paranematic−nematic transition of the LSCE-based composites was verified also in the presence of ferroelectric nanoparticles.