Effects of Cr2O3 doping on the electrical properties and the temperature stabilities of PNW-PMN-PZT ceramics

The ceramics with 0.90Pb(Zr_0.50Ti_0.50)O₃-0.07Pb(Mn_1/3Nb_2/3)O₃-0.03Pb(Ni_1/2W_1/2)O₃ were prepared by adding Cr₂O₃. The effects of Cr₂O₃ doping on the phase structure, the microstructure and the electrical properties of ceramics were investigated. Meanwhile, the temperature stabilities of the resonant frequency (f_r) and the electromechanical coupling factor (K_p) were studied. The results showed that the better temperature stability could be obtained at x = 0.2 wt.% when the calcining temperature was 800 °C and the sintering temperature was 1150 °C. The parameters were Δf_r/f_r25 °C = −0.17% and ΔK_p/K_p25 °C = −1.39%. Moreover, the optimized electrical properties were also achieved, which were K_P = 0.54, Q_m = 1730, d₃₃ = 330 pC/N, ?_r = 2078 and tan δ = 0.0052. The optimized properties make the ceramics with this composition to be a good candidate for high power piezoelectric transformers applications.     

Tantalum influence on physical properties of (K0.5Na0.5)(Nb1−xTax)O3 ceramics

Lead-free (K_0.5Na_0.5)(Nb_1−xTa_x)O₃ ceramics with x = 0.00-0.30 were prepared by the solid-state reaction technique. The effects of Ta on microstructure, crystallographic structure, phase transition and piezoelectric properties have been investigated. It has been shown that the substitution of Ta decreases Curie temperature T_C and orthorhombic-tetragonal phase transition temperature T_O-T, while increasing the rhombohedral-orthorhombic phase transition temperature T_R-O. In addition, piezoelectric activity is enhanced with the increase of Ta content. The ceramics with x = 0.30 have the high value of piezoelectric coefficient d₃₃ = 205 pC/N. Moreover, k_p shows little temperature dependence between −75° C and 75 °C, and d₃₃ exhibits very good thermal stability over the range from −196 °C to 75 °C in the aging test.     

汽车压力传感器的现状和发展

介绍了实用化汽车压力传感器的功能、原理、结构、特点和技术指标。评述和预测了其发展动向。     

Crystallite structure,microstructure, dielectric,and piezoelectric properties of (Pb1.06−xBax)(Nb0.94Ti0.06)2O6 piezoelectric ceramics prepared using calcined powders with different phases

In an attempt to obtain dense lead metaniobate-based ceramics with improved dielectric and piezoelectric properties, the (Pb_1.06−xBa_x)(Nb_0.94Ti_0.06)₂O₆ (x = 0, 0.04, 0.08, 0.12) piezoelectric ceramics were prepared separately from the two kinds of calcined powders, i.e., the powders with the rhombohedral phase and orthorhombic phase. For obtaining the calcined powders with the different phases, two different calcination temperatures of 900 °C and 1250 °C were chosen. The calcined powders were characterized using X-ray diffraction, scanning electron microscope, laser particle size analyzer and differential scanning calorimetry. Effects of the phase structures of the calcined powders on crystallite structure, microstructure, dielectric and piezoelectric properties of the ceramics were studied in detail. The lattice parameters and grain size of the ceramics are related to the phase structures of the calcined powders. The doping of Ba²⁺ has an influence on the dielectric and piezoelectric properties of the ceramics. The ceramics with x = 0.08 fabricated from the calcined powders with the orthorhombic phase demonstrate the optimum dielectric and piezoelectric properties.     

Structural,optical and dielectric studies of novel non-linear Bisglycine Lithium Nitrate piezoelectric single crystal

The novel non-linear semiorganic Bisglycine Lithium Nitrate (BGLiN) single crystals were grown by slow evaporation technique. The structural analysis revealed that it belongs to non-centrosymmetric orthorhombic structure. The presence of various functional groups in the grown crystal was confirmed by FTIR and Raman analysis. Surface morphology of the grown crystal was studied by scanning electron microscopy. The optical studies show that crystal has good transmittance (more than 80%) in the entire visible region and a wide band gap (5.17 eV). The optical constants such as extinction coefficient (K), the reflectance (R) and refractive index (n) as a function of photon energy were calculated from the optical measurements. With the help of these optical constants the electric susceptibility (χ_c) and both the real (ε_r) and imaginary (ε_i) parts of the dielectric constants were also calculated which are required to develop optoelectronic devices. In photoluminescence studies, a broad emission band centered at 404 nm was found in addition to a small band at 352 nm. A broad transition (from 29 to 33 °C) was observed with low dielectric constant value. A high piezoelectric charge coefficient (d₃₃) of 14 pC/N was measured at room temperature which implies its usefulness for various sensor applications. The second harmonic generation efficiency of crystal was found to be 1.5 times to that of KDP. From thermo gravimetric analysis and differential thermal analysis, thermal stability and melting point (246 °C) were investigated. The dielectric behavior, optical characterization, piezoelectric behavior and the non-linear optical properties of the Bisglycine Lithium Nitrate single crystals were reported for the first time which established the usefulness of these crystals for various piezo- and opto-electronics applications.     

Behaviour of piezoelectric lead zirconate titanate irradiating with high-energy xenon ions

The characteristics of a detector fabricated using piezoelectric lead zirconate titanate (PZT) were studied by irradiating it with a 400 MeV/n xenon (Xe) beam while changing the beam flux intensity. The largest output signal was observed from the detector when the beam power per unit time was estimated to be largest. It was also found that the sensitivity per Xe ion of the detector seemed to be higher with decreasing the amount of the Xe ion flux within the limits of the experimental conditions.     

The fine-grained KNN–LN ceramics densified from nanoparticles obtained by an economical sol–gel route

(1 − x)(K_0.5Na_0.5)NbO₃–xLiNbO₃ ((1 − x)KNN–xLN) nanoparticles with the mean particle size about 20–30 nm have been prepared by an economical sol–gel routes using Nb₂O₅ as Nb source. Due to the high sintering ability of nano-particles, fine-grained KNN–LN lead-free ceramics have been densified at the temperature below 1000 °C. X-ray diffraction analysis indicated that the phase structure of the ceramics changed from orthorhombic to tetragonal at x = 0.08–0.10. When the x reached 0.10 and above, the perovskite structure could not be maintained and the impurity phases of K₃Li₂Nb₅O₁₅ and LiNbO₃ appeared, indicating that x = 0.10 is near the solubility limit. Optimized parameters, such as d₃₃ = 170 pC/N and k_p = 0.40, were achieved in 0.90KNN–0.10LN systems. Due to the merits of fine-grained structure and low sintering temperatures, it will be helpful to the application of KNN–LN materials for lead-free multilayer piezoelectric actuator.     

Field-induced strain and polarization response in lead-free Bi1/2(Na0.80K0.20)1/2TiO3–SrZrO3 ceramics

The structure, field-induced strain, polarization and dielectric response of lead-free SrZrO₃-modified Bi_1/2(Na_0.80K_0.20)_1/2TiO₃ (abbreviated as BNKT–SZ100x, with x = 0–0.05) ceramics were investigated. The X-ray diffraction analysis of BNKT–SZ100x ceramics reveals no remarkable change in the crystal structure within the studied composition range. Around critical composition (x = 0.03) at a driving field of 6 kV mm⁻¹, large unipolar strain of 0.37% (S_max/E_max = 617) was obtained at room temperature. The ferroelectric and piezoelectric properties of BNKT ceramics were significantly increased at 2 mol%. At x = 0.02, remnant polarization reached a maximum value of 34 μC cm⁻², while the piezoelectric constant (d₃₃) attained maximum value of 190 pC/N. These results indicate that BNKT–SZ100x ceramics can be considered as promising candidate materials for lead-free piezoelectric actuator applications.     

不同极化态下有机铁电膜微观振动特性的AFM研究

借助原子力显微镜优异的空间分辨能力和锁相放大技术,实验研究了有机铁电薄膜在不同极化状态下的微观振动特性.负极化态时,薄膜表面振动与驱动电压呈线性且同相;而正极化态时,表面振动与驱动电压依然呈线性,但两者间存在180°相差.实验中清楚地观测到局域振动畴、非振动畴以及振动振幅相对较小的振动畴三者间的共存.本工作探讨了非活性铁电畴存在的可能性,并认为是陷阱电荷的箝制作用限制了铁电畴的活性.     

Fabrication of lead-free (Na0.82K0.18)0.5Bi0.5TiO3 piezoelectric nanofiber by electrospinning

(Na_0.82K_0.18)_0.5Bi_0.5TiO₃ nanofibers were synthesized by sol-gel process and electrospinning. Scanning electron microscopy was used to verify that the diameters and lengths are in the range of 150-600 nm and several hundreds of micrometer. Perovskite structure and grain size (20-70 nm) were verified by X-ray diffraction and transmission electron microscopy. The high effective piezoelectric coefficient d₃₃ (96 pm/V) was measured by scanning force microscopy. It may be attributed to easily tilting the polar vector of domain for an electric field and the increase in the number of possible spontaneous polarization direction near the rhombohedral-tetragonal morphotropic phase boundary. The research shows that there are potentional applications for (Na_0.82K_0.18)_0.5Bi_0.5TiO₃ nanofiber in nanoscale lead-free piezoelectric devices.