ИСТИНА

Strong demands of various industries simulated search for new piezoelectric materials for high temperature applications. To improve sintering and regulate functional properties, various approaches were used, however, till now functional properties of new perovskite-type materials do not compete with those of the PZT-based materials. In this work, structure, microstructure, dielectric and piezoelectric properties of oxides based on the (1-x)BiScO3 - xPbTiO3 (BSPT) with x = 0.63-0.65, and K0.5Na0.5NbO3 compositions close to the Morphotropic Phase Boundary were studied. In order to regulate functional properties, modification of cation compositions, addition of overstoichiometric additives (MnO2, chlorides KCl, NaCl, CaCl2 and fluoride LiF) and optimization of preparation conditions were performed. The samples were prepared by the solid state reaction method. Phase formation, structure parameters and functional properties were studied using the X-ray diffraction, SEM, SHG, and Dielectric Spectroscopy methods. Piezoelectric parameters d33 and kt of the preliminary poled samples were measured.Optimal sintering conditions of dense and textured ceramics preparation were determined. The variations of relative contents of tetragonal and rhombohedral phases, structure and microstructe parameters, dielectric and piezoelectric properties were observed depending on composition and thermal treatment conditions. The 1st order phase transitions were observed for all samples at high temperatures ~ 700 – 1000 K. The changes of the TC values correlated with the changes in the unit cell parameters and relative phase content caused by doping. High piezoelectric coefficients d33 up to ~ 500 pC/N and kt ~ 0.65 values were measured in the BSPT ceramics prepared. Enhancement of piezoelectric properties will be discussed in relation to the preparation conditions, type and content of dopants.