Papers by Keyword: Piezoelectric Properties

Abstract: The application of piezoelectric polyvinylidene fluoride (PVDF) has become of a great interest. Due to its piezoelectric properties, PVDF is used in various applications, namely, microdevices and sensors. Electrospinning was found to be the most suitable and efficient method to synthesis PVDF nanofibers. It is used to obtain PVDF nanofibers without additional mechanical stretching and with high β phase content. For these reasons, it is considered to be an economic technique. In the present paper, the parameters affecting the synthesis of PVDF nanofibers such as solution concentration, flow rate, voltage and Tip to Collector Distance (TCD), have been investigated. The optimum conditions were found to be 18% concentration, 15 cm TCD, 1 mL/h flowrate and 19 kV voltages. The fabricated nanofiber has been characterized using SEM, FTIR, XRD and a conductivity test.

Abstract: The ferroelectric solid solutions described by a general formula 0.98Pb(Zr_1-xTi_x)O₃ – 0.02La(Fe³⁺_0.5, Nb⁵⁺_0.5)O₃ have been obtained by solid state reaction technique, where x assumes the following values: 0.42, 0.48 and 0.58. The structure of these ferroelectric compositions has been investigated in detail using X-ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM). The results obtained by XRD have evidenced that all obtained samples have a perovskite structure. The influence of the sintering temperature on the degree of incorporation of the elements in the solid solution have been studied too. The dielectric and piezoelectric constants have been determined and the influence of temperature on obtained values are presented and discussed. The performed experimental results have pointed out that the materials are characterized by a high anisotropy. Furthermore, the obtained values of the electromechanical coupling factor (k_p) is situated between 0.40÷0.65 depending on the composition and the sintering temperature too.

Abstract: Ba_0.85Ca_0.15Ti_0.9Zr_0.1O₃ (BCTZ) ceramics, one of the lead-free pizoelectric materials, were focused due to the environmental concern against lead. A modified BCTZ powder sol-gel fabrication process was experimentally introduced with the addition of glycerol, in order to provide an effective approach to optimize the piezoelectric response of BCTZ ceramics. The results showed that the piezoelectric properties enhanced in terms of the piezoelectric coefficient of d₃₃, 510 pC/N and the electromechanical coupling coefficient of k_p, 0.501. The enhancement in electrical properties, such as dielectric, ferroelectric and piezoelectric, could be related to the homogenous microstructure and larger grain size of BCTZ ceramic powders after the introduction of glycerol during the modified sol-gel strategy.

Abstract: The aims of present study were investigated the effect of nickel doping on the dielectric and piezoelectric properties of P(BN)ZT solid solution. P(BN)ZT powder doped with nickel nanoparticle in the composition of (1-x) PBNZT–xNi when x = 0, 2, 4, 6, 8 and 10 percent by mole. P(BN)ZT doped with nickel powder were calcined at 900 °C for 2 h and sintered at the temperature range of 1150 -1250°C for 2 h with heating/cooling rate of 5 °C/min. The dielectric constant (e_r) and the dielectric loss tangent (tand) of all ceramics were measured at room temperature using LCR meter. The piezoelectric properties (d₃₃) were measured at room temperature using d₃₃ meter. The micro and nano-domain structure was clearly observed by piezo-response force microscopy (PFM). From the results, it can be seen that the dielectric and piezoelectric decreased with increasing Ni particle of all composition (0.0-0.1 mol%). Moreover, PFM images show that the micro (180°) and nano (90°) domain are orientated at the surface region in submicron-scale of P(BN)ZT ceramics with doped nickel nanoparticle.

Abstract: Some piezoelectric properties of lead zirconate titanate PbZr_0.53Ti_0.47O₃ ceramic samples sintered at 1100oC for 3 hours has been investigated in this work and compared to the strontium modification at 0.2, 0.4, and 0.6 mol%. Polarization versus Electric Field curve and d₃₃ and K_p piezoelectric parameters was taken at room temperature in order to investigate the correlation with phase amount and lattice parameters of crystalline phases calculated through Rietveld refinement. The results indicated the lead substitution with 0.4 mol% of strontium enhances the d₃₃ and K_p piezoelectric parameters, but there is no systematic variation of the piezoelectric properties with strontium content. By the other hand, tetragonal phase seems plays an important rule on piezoelectric devices operating near the room temperature and some correlations could be found.

Abstract: A strong desire for environmental protection and human health care urgently requires us to find an environmental friendly type of piezoelectric material to replace the lead ones. In this study, (Li_xK_0.5-xNa_0.5)(Nb_0.97Sb_0.03)O₃-1mol%CuO (x = 0, 0.05, 0.1 ,0.2 ,0.5, abbreviated as CuO-L_xKNNS) lead-free piezoelectric ceramics have been fabricated by a conventional solid-state reaction route. We focused on the comparison of buried powder sintering with exposed sintering. The effect of buried powder sintering method on density, structure and dielectric, piezoelectric properties of CuO-L_xKNNS ceramics has been investigated. It was found that the density increased greatly when the buried powder sintering method was used, which was effective in inhibiting the volatilization of alkali metal oxides compared with exposed sintering method. Piezoelectric and dielectric properties showed a similar tendency with the density. These ceramics showed an obvious phase transition with increasing the Li content. CuO-L_xKNNS ceramics showed orthorhombic symmetry when x= 0, but turned to be tetragonal symmetry when x ≥ 0.05. The optimal composition of CuO-L_xKNNS with buried powder sintering method was x = 0.05 sintered at 1020 °C, for which the maximum value of the piezoelectric constant (d₃₃) was 180pC/N, the density (ρ) was 4.40g/cm³, the room temperature relative dielectric constant (ε_r) was 270 and the dielectric loss (tanδ) was 0.07.

Abstract: 0.998[(0.95(K0.5Na0.5)NbO₃-0.05LiSbO₃]-0.002BiFe_1-xCo_xO₃ (KNN-LS-BF_1-xC_x, x=0-0.8) piezoelectric ceramics were prepared by solid-state reaction method. The influences of Co content on piezoelectric and ferroelectric properties were investigated. The results reveal that the substitution of Co significantly affects the piezoelectric and ferroelectric properties of KNN-LS-BF_1-xC_x ceramics. All samples with various Co contents show a pure perovskite structure. With increasing x from 0 to 0.8, the depolarization temperature T_d of KNN-LS-BF_1-xC_x ceramics increase with increasing x, and the piezoelectric constant d₃₃ of KNN-LS-BF_1-xC_x specimen with x=0.2 is larger than those of other KNN-LS-BF_1-xC_x specimens in the investigated range when the temperature is lower than T_d. The remnant polarization P_r decrease with x in the investigated range, but the coercive field E_c increase to 1.78kV/mm with x up to 0.6, and then decrease with further increase of Co contents x.

Abstract: A layer of ZnO thin film was deposited repetitively 15 times on a silicon substrate by sol-gel spin coating technique. The structural and electrical characteristic of the thin film was studied and presented. For structural characterization, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analysis were chosen while Semiconductor Parametric Analyzer (SPA) was used to measure the electrical characteristic. The ZnO thin film thickness were measured to be between 165 nm to 180 nm. The resistance increased proportionally with annealing temperature with the lowest value of 80Ω. Structurally, the grain sizes of the ZnO thin films increased with the increase in annealing temperature. The root mean square (RMS) and average surface roughness (Ra) were measured respectively.

Abstract: In this paper, the sol-gel method was used to systematic study of the preparation conditions and sintering conditions about KNN-0.008BF powders. At the same time, microstructure and electrical properties of ceramics were studied and analyzed. In this experiment, citric acid(CA) as metal chelator, ethylene glycol(EG) as esterification and chelating agents. Through a large number of experiments, n(citric acid):n(ethylene glycol)=2:1, n(citric acid):n(Nb⁵⁺)=1.5:1 is the best equipped ratio. This ratio can obtained pale yellow transparent solution. Under the experiments condition, PH of the precursor solution and the sintering temperature of powders have great influence on experimental. Experiments confirmed that PH=5-6 and temperature=1100°C is the best preparation condition, in which condition piezoelectric ceramics can obtained excellent structures and piezoelectric properties.

Abstract: It is well known that piezoelectric ceramics are wildly used in many fields such as electrical sensors, actuators, alarm equipments etc. In this paper，the microstructure and the piezoelectric properties of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 (PMNZT) were studied. A novel B-site precursor method was adopted for preparing of Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples. For investigating the crystallographic phase and microstructure of the samples, X-ray diffraction(XRD) and scanning electron microscopy(SEM) methods have been adopted respectively. The results show that a pure perovskite structure can be obtained after sintering at 1220°C for 2h. Through this experiment, it has been found that when sintering at 1220°C for 2h and the amounts of the Pbx（Nb2/3Mg1/3）xO3 (PMN) is 0.14, the Pb（Zr1/2Ti1/2）1-x（Nb2/3Mg1/3）xO3 samples are with the best electrical properties as follows: dielectric constant (ε) is 1858, dielectric loss(tanδ) is 0.017, electromechanical coupling coefficient (Kp) is 0.515, piezoelectric constant(d33) is 362PC/N