Growth And Dielectric, Piezoelectric Properties Of K_1-xNa_xTa_1-yNb_yO₃ Signle Crystals

Since Curie found the piezoelectric effect from alpha quartz material, piezoelectric materials were widely used in many aspects, for example, piezoelectric transformer, standard signal source, electroacoustic transducer, ultrasonic transducer, acoustic transducer, pressure gauge, filter, amplifier, surface waveguide, infrared detector, lightning acousto-optic modulator, and so on. Ferroelectrics were divided into perovskite ferroelectric, tungsten bronze ore type ferroelectric and lithium niobate type ferroelectric, according to the structural features. Eventually, because of the larger piezoelectric coefficients, lead zirconate titanate(PZT) ferroelectric piezoelectric coefficient(d33) dominated in the field of piezoelectric and ferroelectric. Recent years, researchers began to pay more and more attention to environmental protection, and a large number of lead-free piezoelectric materials research generally proved that KNNbased piezoelectric materials had great potential instead of lead piezoelectric materials.First, tantalum potassium sodium niobate single crystals(K1- xNaxTa1- yNbyO3, x = 0.70, 0.64, 0.61, respectively, y = 0.63, 0.60, 0.58, abbreviated as KNTN) were grown using top-seed solution growth method. Basic principle of KNTN single crystal growth were introduced, and the KNTN segregated characteristics in process of crystal growth was studied. The relationship between K and Na segregated with Ta and Nb segregated was studied.Secondly, dielectric and ferroelectric properties of as-grown KNTN single crystals were measured. The structure of KNTN single crystals were tested by X-ray diffraction analysis(XRD), and the crystals were orientated by Laue X-ray machine after structure determined. Then, the surface of the(001)c were covered by silver electrodes, the temperature dependence of the dielectric constant along the [001]c of KNTN single crystals were measured, and TO-T and TC of the KNTN single crystals were determined. The electric hysteresis loop of single crystals and leakage currents were measured by ferroelectric test system.Finally, the method of all matrices parameter about 4mm point group were studied. The as-grown KNTN single crystals was poled, and the frequency dependency of impedance of KNTN single crystals were tested using impedance analyzer, and the resonant frequency of piezoelectric vibrators were determined by LCR, and the complete parameters of KNTN single crystal were calculated. Then, though comparing the internal energy of KNTN single crystal at tetragonal phase and orthorhombic phase, the reason of the excellent property of K0.39Na0.61Ta0.42Nb0.58O3 single crystal was obtained.