Papers by Keyword: Piezoelectric

Abstract: 0.67BiFeO₃-0.33BaTiO₃ thick films were prepared by screen printing pastes prepared by kneading the 0.67BiFeO₃-0.33BaTiO₃ powder in a three-roll mill with an organic vehicle. The thick films were fired with Pt bottom electrodes and ZrO₂ substrates to investigate the influence of firing temperature. The microstructures and ferroelectric properties of the thick films were examined and compared with the bulk ceramics. A remanent polarization of 32.0 μC/cm² and coercive field of 28 kV/cm were obtained for a thick film with the addition of 0.5 wt% MnO that was fired at 1050 °C.

Abstract: Generally, force measurement of nanoscale material widely employs a quartz tuning fork which is resonant mechanical sensors on 32.768 kHz resonance frequency and is powerful tools. But, this paper designs the sensor by using tuning fork on 3 kHz and modifies the tuning fork by a tiny pin adhesive into the end of prong. In experiment, measurements of electrical signal from piezoelectric are study of load-mass effect and pin position. 2 touching techniques are considered: a shear-force type and a tapping mode type with highly position movement system. Silicone rubber, vinyl eraser and hydrogel are elastic material for testing. Results show that both weight and position of pin is significant influencer for resonance frequency and quality factor of sensor. Finally, the tuning fork response experimentation shown this method can be applied to material classification.

Abstract: Lateral field excitation (LFE) acoustic wave devices, which employ two electrodes on the same surface of a piezoelectric substrate, have been found attractive in sensing applications. However, up to now, the sensitivities of pure-LFE devices based on LiNbO₃ single crystal is unknown. In this work, the effective LFE exciting electric field direction of (yxl)89° LiNbO₃ is determined. The calculated results showed that when the driving electric field direction is perpendicular to the crystallographic X-axis of the piezoelectric substrate, (yxl)89° LiNbO₃ LFE device works on pure-LFE mode. Based on this, several LiNbO₃ pure-LFE bulk acoustic wave sensors with three different electrodes are designed and fabricated. The results show that the (yxl)89° LiNbO₃ LFE sensor with interdigital electrodes is 11.1 times and 2.2 times more sensitive to changes in liquid conductivity compared to traditional LFE devices with single gap circular electrodes and Archimedes spiral electrodes, respectively. The results are important for investigating high-sensitivity LFE bulk acoustic wave sensors by using LiNbO₃ single crystal.

Abstract: A low frequency energy harvesting structure was studied, describing the process of its manufacture. The natural frequency was obtained by modal analysis of the structure. It obtained the relationship between the magnitudes of the voltage generated from the piezoelectric energy harvesting device and the size parameters of structure, so that the energy harvesting structure can operate at the resonant frequency in order to obtain the maximum energy.

Abstract: Barium - Strontium Hexaferrite and Barium Strontium Titanate are both well established materials which widely used respectively as permanent magnets and piezoelectric devices. As the properties are a structure sensitive, materials structure as well as crystal structure must be properly designed to meet a specific application. In this paper, we report our recent investigation on material structure analysis of Ba_0.3Sr_0.7Fe₁₂O₁₉ and Ba_0.7Sr_0.3TiO₃ composite system prepared by a mechanical alloying process to promote feroic properties. The average of particle size for composites system was found initially increased to a large size of 9 μm after mechanically milled for 30 hours and then start to decreased to smaller size of ~ 5μm when the milling time was extended to 80 hours and showing trend toward further reduction in mean particle sizes. In the latter case, the XRD trace for milled powders showed broadened diffracted peaks pattern due to deformation during mechanically milling. After sintering at a temperature of 1050 °C much finer crystallites of 7-13 nm size in a dense pellet were observed. Hence, sintering to the milled particles has promoted formation of nanocrystal containing particles. The mean crystallite size for magnetic phase was about more than 350 times smaller than the mean particle size of composite particles. Finer crystallite sizes were found in B₃SF in which the mean was about 700 times smaller than the mean particle size. The magnetic and electric properties of the composite system are also discussed.

Abstract: To meet the demand of rotating mechanism for self-powered monitoring system, piezoelectric energy generator (PEG) excited by the magnetic coupling force between rotating magnets fixed on a rotator and those fixed on piezo-beam was presented. The influence of magnetic force (number and configuration of the magnets) and rotating speed on energy generation of the PEG was investigated experimentally. The research results show that there are several optimal rotating speeds for the PEG to achieve peak voltage at speed range of 0 to 1390r/min. Under a given number of magnets fixed on the end of the piezo-beam, the peak voltages rise with the increasing of rotating magnets number and rotating speed. At 636r/min, the achieved peek voltages from the PEG with 1/2/4 rotating magnets are 12.1/15.2/20.0V respectively. Besides, the configuration modes of rotating magnets and the fixed magnets (repulsion, attraction, or repulsion-attraction) exert great influence on the peak voltage and the relative optimal rotating speeds. Taking a PEG with 2 rotating magnets for example, the 4th peek voltages and the relative optimal rotating speeds for the PEG under exciting mode of repulsion/attraction//repulsion-attraction are 12.6/15.0/16.4 V and 552/528/492 r/min respectively.

Abstract: To meet the demands of the rotating structure for self-power, a novel gyromagnetic piezo-cantilever generator (GPCG) excited by the coupling between rotating magnets and those fixed on piezo-cantilever was presented. The influence of magnetic force (number and configuration of the magnets) and rotating speed on energy generation of the GPCG was investigated experimentally. The research results show that there are 9 optimal rotating speeds for the GPCG to achieve peak voltage at speed range of 0-1390r/min. With 1 magnet (ø12x2mm³) fixed on piezo-cantilever, the increasing number of rotating magnets (ø12x4mm³) in the same place (n_s) of the rotator exerts no influence on the optimal rotating speeds, but leads to rising output voltage. At 1042.5r/min, the achieved peak voltages from the GPCG in the case of n_s=1/2/4/6 are 13.2/16.6/23.8/27.8V respectively. The optimal speeds decrease and the peak voltage rises with the increasing number of magnets evenly distributed on the rotator (n_d). In the case of 1 magnet fixed on piezo-cantilever and n_d=1/2/4/8, the optimal rotating speeds and the peek voltages from the GPCG are 708.9/528.2/528.2/264.1r/min and 13.2/16.6/23.8/27.8V respectively.

Abstract: 0.95 (K_XNa_1-X) NbO₃-0.05 LiSbO₃ (KNN-LS-X) (X=0.4-0.5) lead-free ceramics were prepared by conventional solid method. The effect of K/Na ratio on the dielectric, piezoelectric, pyroelectric and polymorphic phase transition was studied. The results show that the electrical properties strongly depend on the K/Na ratio. The KNN-LS-X(X=0.45) ceramics exhibit enhanced properties (ε_r=891.267, d₃₃=222pC/N, K_p =0.43517, Q_m=64.72, p=15×10^-4C/m²K). Enhanced electrical properties of the KNN-LS-X (X=0.45) ceramics could be attributed to the effect of K/Na ratio modifying the polymorphic orthorhombic-tetragonal phase transition temperature to room temperature, which could make KNN-LS-X (X=0.45) ceramics use as a new ferroelectric sensor.

Abstract: The study investigates piezoelectric harvesting efficiency of BTO microstructures with different structural configurations for electromechanical nanogenerators using FEM simulation. The effects of different BTO structures in same cross-section area are simulated, including the lengths, the heights, array numbers, shapes and harmonic response. The results show that a single-bulk structure of piezoelectric BTO produces less harvesting energy than an array structure in same cross-section area. The harvesting voltages increase with array number increasing. However, the energy harvesting obviously decreases when the array number is over 33. There has lager energy harvesting with a small ratio (R_h) that defined a diameter of BTO cylinder devided by a height of BTO cylinder. In addition, the piezoelectric harvesting based on BTO arrays with a zigzag layer has higher harvesting efficiency.

Abstract: A tuning fork with piezoelectric (TFP) is an electro-mechanical device; its principle performance is based on specific frequency and limited voltage. As the principle, the device can result output significantly. This paper presents a material classification using phase difference value that is received from touching between material and modified TFP. For the modified TFP, it is customized by a millimeter needle. The frequency response method on Bode plot is used to observe the modified TFP behavior, and to select a specific frequency. The first-order model with cascade notch filters is employed to identify mathematical model of the TFP, and to verify the model by simulation. Experimentation is considered on 2 touching techniques: a shear-force type and a tapping mode type. There are hard plastic, iron, silicon rubber, vinyl eraser and hydrogel for test material. The results are described by both time series plots of input-output signals and numerical table of shifted phase. The technique can employed to classify the test materials effectively and explicitly.