Preparation And Electrical Properties Of Lead-free /lead-less Piezoelectric Material

Ceramics (1-x)Bi_0.47Na_0.47Ba_0.06TiO_3-x-xKNbO₃(BNBT-xKN, x=0⁰.08)were prepared by ordinary solid-state ceramic processing. The effects of KNbO₃ on the microstructure, dielectric properties and phase transition of BNBT-xKN were investigated using X-ray diffraction, scanning electron microscope (SEM), impedance analyzer and ferroelectric analyzer. The results shows that KNbO₃ (KN) diffuses into the lattice of (1-x)Bi_0.47Na_0.47Ba_0.06TiO_3-x to form a solid solution with pure perovskite structure. The SEM morphology of BNBT-xKN ceramic shows that moderate KN can homogenize the grain size of the BNBT_-xKN ceramics. The dielectric constant vs. temperature spectrum (30⁵00℃) shows that three dielectric abnormal peaks have been observed in the BNBT, BNBT-0.01KN, BNBT-0.02KN ceramics, and only two abnormal peaks have been observed in BNBT-0.04KN and in the BNBT-0.08KN ceramics. In this work, the relax properties of BNBT_-xKN is discussed by fitting the dielectric constant vs. temperature spectrum. The mechanism of depolarization and the double hysteresis loop of BNBT_-xKN are distributed.Hot press and cold press molding were used to prepare the 0-3 ferroelectric PMN-PT/PVDF composite. The piezoelectric single crystal 0.7Pb(Mg_1/3Nb_2/3O₃-0.3PbTO₃ (PMN-PT) with high piezoelectric properties was grown by Bridgman method. The PMN-PT crystal powder was embedded into polyvinylidene fluoride (PVDF) polymer by heating the mixture of PMN-PT and PVDF power. The mass content of PMN-PT powder in the composite ranges from 50% to 90%, the results shows the dielectric constant and piezoelectric coefficient increase with the PMN-PT mass content. The highest piezoelectric constant and dielectric constant achieves 42.4 pC/N and 95, respectively. The polarization mechanism is used to explain the effect on piezoelectric and dielectric properties base on measurement of polarization vs. electric field loop and dielectric constant. SEM was used to observe the surface morphology of the PMN-PT/PVDF composite. The density of composite prepared with hot press molding is higher than prepared with cold press molding.