| As development of atomic energy, aerospace, automotive, metallurgy and petrochemical, the use of the device has made more demanding requirements. In high temperature environment, it is widely used to study the electronic components of piezoelectric ceramics which can work stably in high-temperature. The(1-x)BiFeO3-xBa TiO3(BF-x BT) based lead free piezoelectric have been fabricated by conventional solid-state method. It has excellent piezoelectric properties, high-temperature thermal stability and is easy to prepare, thus expected to applied widely in high-temperature working environment. In this paper, the composition, microstructure, electrical properties and high-temperature stability were investigated systematically, and the influence of substitution and doping on the ceramics was also examined. Several important conclusions can be summarized as follows:The relation between composition and crystalline structure, microstructure, dielectric properties, piezoelectric properties of BF-xBT ceramics was systemically investigated. The results of XRD showed that the crystalline structure of the BF-xBT ceramics is rhombohedral with x=0.27~0.32 and is pseudo-cubic structure with x at 0.34. The grain size of the ceramics decreases with the increase of BT content. The largest piezoelectric constant(d33=135pC/N) was obtained at x=0.29. The Curie temperature Tc of BF-xBT ceramics decreased with the increasing of BT. As x increased from 0.34 to 0.27, the Tm decreased from 449 oC to 389 oC. With increasing content of BT, the dielectric constant ?r and dielectric loss tan? both increased. The influence of polarization on the crystal structure and dielectric properties of BF-xBT ceramics was studied by using ex-situ measurements. The results of XRD showed that the polarization can change the(003)/(021) direction diffraction peak intensity of the ceramics. Polarization make the dielectric permittivity ?r and dielectric loss tan? increasing. Meanwhile, the Curie temperature of the ceramics will be improved by polarization, at x=0.27, Tm increased 449 oC to 485 oC. The polarization electric field strength can increase the temperature stability of the ceramics.The effect of doping of LiNbO3(LN) in BFBT ceramics on crystalline structure, microstructure, dielectric properties, piezoelectric properties was investigated. The results of XRD showed that with increasing LN content, the structure transform from rhombohedral to pseudo-cubic structure. SEM showed that the addition of LN decreased the grain size and increased in density of ceramics. The largest piezoelectric constant(d33=152pC/N) and the largest electromechanical coupling factor(kp=0.25) was obtained at x=0.6%. With the increase of LN content, the Curie temperature Tc decreased. Polarization increase the dielectric permittivity ?r and dielectric loss tan? of the ceramics. Polarization increase Tc. Poor temperature stability of piezoelectric properties of BFBT-xLN ceramic, the depolarization temperature decreases with the increase of LN content. The strong polarized electric field might enhance the piezoelectric properties temperature stability at x=0.6%. It is found that the strain value(Strain%) and the negative strain decrease with the increase of x, at x=1.2%, the negative strain value is approximately 0.With the increase of BT content, the dielectric dispersion and relaxation feature of BF-xBT ceramics were increased. With increasing of LN content, the dielectric dispersion and the relaxation characteristic were increased. The relaxiton behavior of BFBT-xCu ceramics is different with conventional relaxor ferroelectrics. With the increase of Cu content, the BFBT-xCu creamics transformation from relaxation ferroelectric to normal ferroelectric. |
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