Growth, Structure And Properties Of Pseudo-ternary Relaxor Ferroelectric Crystals

Relaxor-PbTiO3ferroelectric single crystals with the morphotropic phase boundary (MPB) exhibit the excellent properties, such as higher piezoelectric coefficients, higher dielectric permittivity, higher electro-mechanical coupling factor, higher field induced strain, higher pyroelectric and acousto-optic properties. These single crystals have attracted considerable attention for their potential applications of high performance underwater acoustic transducers, medical ultrasonic transducers, piezoelectric actuators, pyroelectric detectors and ultrasonic wave devices in various industrial and scientific areas. However, the application of PMN-xPT single crystals in high temperature and electric filed conditions is limited to the depolarization due to the lower rhombohedral-tetragonal phase transition temperature (60-80℃) and lower coercive field (2kV/cm). In addition, properties of the crystals are decreased with the existence of pyrochlore phase in crystal. Therefore, Relaxor1-Relaxor2-PbTiO3relaxor ferroelectric single crystals with the MPB was build. PSN-PMN-PT crystals were obtained by high temperature solution method and Bridgman method. The morphology, growth mechanism and electrical properties of the crystals were observed and characterized.1. Five components crystals (A, B, C, D and E) were obtained by high temperature solution method. Most crystals show pure perovskite structure with color of light yellow and pseudo-cubic shape. Maximum size of the crystals is about4mm. There are less pitting corrosions with size of several microns in crystal surface. A large number of growth steps with size of200nm arrange orderly in crystal. The growth mechanism of the crystals is layer growth mechanism controlled by two-dimensional nucleation. Dielectric permittivity and dielectric loss are2285-5216and0.024-0.150for the crystals. Piezoelectric coefficients are820-1454pC/N. Coercive field are4.05-4.98kV/cm. The rhombohedral-tetragonal phase transition temperature and the Curie temperature are90-11℃and149-158℃, respectively.2. F component single crystals with color of light yellow and size of (P25x50mm were obtained by Bridgman method. The crystals are pure perovskite structure. Dielectric permittivity and dielectric loss are1100-6200and0.019-0.081for the crystals. Piezoelectric coefficients are428-2290pC/N. Coercive field are4.03-6.29kV/cm. The rhombohedral-tetragonal phase transition temperature and the Curie temperature are67-75℃and130-158℃, respectively.3. Both of the rhombohedral-tetragonal phase transition temperature and coercive field of PSN-PMN-PT relaxor ferroelectric crystals are higher than that of the PMN-xPT relaxor ferroelectric crystals. PSN can increase the stability of perovskite phase and suppress the formation of pyrochlore phase.