Piezoelectric Single Crystals Research Articles

Bandwidth-broadening properties by using a variable width structure in a cantilever-type piezoelectric energy scavenger

In this paper, we present the simulation and the experimental results for vibration-energy-scavenging performances in a cantilever-type piezoelectric energy scavenger with bandwidth broadening properties by using a variable width structure. Using the measured mechanical damping ratio and electro-mechanical coupling coefficient of the fabricated cantilever-type device, we simulated the output performances and designed a cantilever-type piezoelectric energy scavenger with bandwidth broadening characteristics. A device based on a parallel-bimorph cantilever structure with a proof mass, which was designed to have a natural resonance frequency of about 60 Hz, and the energy-scavenging capability of a piezoelectric single crystal was measured and compared them with the simulated results. The results showed that several tens of ac volts and a few milliwatts of power were achieved under a 0.1 grms vibration condition with a 3 Hz bandwidth.

Shape-controlled crystal growth of Sr3NbGa3Si2O14 and Sr3TaGa3Si2O14 piezoelectric crystals by the micro-pulling-down method

We grew column-shaped Sr(3)NbGa(3)Si(2)O(14) (SNGS) and Sr(3)TaGa(3)Si(2)O(14) (STGS) langasite-type piezoelectric single crystals by the micro-pulling-down (μ-PD) method. 3-mm-diameter SNGS and STGS crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die. According to X-ray rocking curve measurements, the grown crystals had crystallinity equivalent to that of crystals grown by the Czochralski (Cz) method. The crystals were single-phase materials with langasite-type crystal structure. The lattice parameters of the grown crystals were almost consistent with those of crystals grown by the Cz method.

Shaped crystal growth of langasite-type piezoelectric single crystals and their physical properties

We have grown shape-controlled langasite-type crystals by the micro-pulling-down (μ-PD) method. Columnar shaped La(3)Ta(0.5)Ga(5.5)O(14) (LTG), Ca(3)NbGa(3)Si(2)O(14) (CNGS), Ca(3)TaGa(3)Si(2)O(14) (CTGS), Sr(3)NbGa(3)Si(2)O(14) (SNGS), and Sr(3)Ta- Ga(3)Si(2)O(14) (STGS) crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die at the bottom. All grown crystals showed high transparency except for the peripheral area and diameter of approximately 3 mm. The chemical phases at the central parts of the grown crystals were identified as a single phase of langasite-type structure and their lattice parameters were almost the same as those of crystals grown by the Czochralski (Cz) method; however, some impurity phases were observed in the peripheral area. In X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by the Cz method. The piezoelectric constant d(11) of the CNGS crystal was 3.98 pC/N; this value is well correlated with those of previous reports.

Evaluating transducer bandwidth and effectiveness on overall acoustic system performance

Piezoelectric ceramic cylindrical transducers are used extensively for underwater acoustic communication applications on mobile platforms (UUVs). Employing piezoelectric single crystals, used in either fully-active or active-passive segmented cylinders, in the transducer design has the potential to increase the usable bandwidth while reducing the overall size and weight of the device. In some instances, one single crystal transducer may replace several ceramic transducers and reduce the number of hardware channels. The impact on acoustic system design (power amplifier, matching transformer, and tuning network) for several piezoelectric ceramic and single crystal cylindrical transducer technologies is modeled and supported with measured transducer data.

Electromechanical nonlinearities and losses in piezoelectric sonar transducer materials

Next-generation sonar projectors rely on piezoelectric single crystals such as lead magnesium niobate-lead titanate to induce mechanical strain and generate ever greater acoustic output, but the performance of these materials under high-power operation is not well understood. As the electrical driving force increases, the linear piezoelectric relationships give way to nonlinear, amplitude-dependent properties. Such behavior is impossible to predict solely from small signal, linear measurements. This work has characterized the behavior of single crystals by examining the dynamic relaxation from initial strain levels of 0.1 to 0.2%. Strain-dependent values of the mechanical quality factor and resonance frequency are reported for single crystals, and these properties are compared with conventional high-power piezoceramics.

High-frequency PIN–PMN–PT single crystal ultrasonic transducer for imaging applications

A high-frequency (∼60 MHz) ultrasonic transducer with a [001]-oriented 0.27Pb(In1/2Nb1/2)O3–0.45Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 (PIN–PMN–PT) piezoelectric single crystal as an active element has been fabricated and characterized. The poled PIN–PMN–PT single crystal has thickness mode electromechanical coefficient kt of 0.56 and piezoelectric constant d33 of 1550 pC/N. The −6 dB bandwidth of the transducer is 73 % and the insertion loss at its centre frequency is −20 dB. With the study as a function of temperature, the PIN–PMN–PT transducer shows better thermal stability than the binary single crystal transducer. Furthermore, the transducer was evaluated using a 30-μm aluminum wire phantom image, in which the −6 dB axial and lateral resolutions are found to be 26 μm and 127 μm, respectively. Ultrasonic images of fish eyes were obtained with the 60-MHz transducer. It is shown that the high-sensitivity transducer can produce the images with high signal-to-noise ratio and good contrast.

Bending strength of piezoelectric ceramics and single crystals for multifunctional load-bearing applications

The topic of multifunctional material systems using active or smart materials has recently gained attention in the research community. Multifunctional piezoelectric systems present the ability to combine multiple functions into a single active piezoelectric element, namely, combining sensing, actuation, or energy conversion ability with load-bearing capacity. Quantification of the bending strength of various piezoelectric materials is, therefore, critical in the development of load-bearing piezoelectric systems. Three-point bend tests are carried out on a variety of piezoelectric ceramics including soft monolithic piezoceramics (PZT-5A and PZT-5H), hard monolithic ceramics (PZT-4 and PZT-8), single-crystal piezoelectrics (PMN-PT and PMN-PZT), and commercially packaged composite devices (which contain active PZT-5A layers). A common 3-point bend test procedure is used throughout the experimental tests. The bending strengths of these materials are found using Euler-Bernoulli beam theory to be 44.9 MPa for PMN-PZT, 60.6 MPa for PMN-PT, 114.8 MPa for PZT- 5H, 123.2 MPa for PZT-4, 127.5 MPa for PZT-8, 140.4 MPa for PZT-5A, and 186.6 MPa for the commercial composite. The high strength of the commercial configuration is a result of the composite structure that allows for shear stresses on the surfaces of the piezoelectric layers, whereas the low strength of the single-crystal materials is due to their unique crystal structure, which allows for rapid propagation of cracks initiating at flaw sites. The experimental bending strength results reported, which are linear estimates without nonlinear ferroelastic considerations, are intended for use in the design of multifunctional piezoelectric systems in which the active device is subjected to bending loads.

Engineered domain configuration and piezoelectric energy harvesting in 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals

The performance of cantilever piezoelectric energy harvesters using three types of piezoelectric materials, relaxor ferroelectric 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystals oriented along the 〈110〉 and 〈001〉 directions, and a PZT-based ceramic, were investigated. The 〈110〉 and 〈001〉 oriented PMN-PT single crystals, which have a rhombohedral phase and spontaneous polarization along the 〈111〉 direction, presented electromechanical coupling factor k31’s of 0.78 and 0.42, respectively. The cantilever-type energy harvester operated by 31 resonance mode generated a larger output power of 1.07 mW for the 〈110〉 oriented PMN-PT single crystal compared to those of the other materials. The effective electromechanical coupling factor of the piezoelectric energy harvester with the 〈110〉 oriented crystal also reached 0.25, not achievable with the other piezoelectric materials. These results demonstrate that the domain engineering of the piezoelectric single crystals can provide higher design flexibility for a tiny energy harvester.

Lead-free piezoelectric single crystal based 1–3 composites for ultrasonic transducer applications

In this work, lead-free 1–3 composites based on piezoelectric 0.947Na0.5Bi0.5TiO3–0.053BaTiO3 (NBT–0.053BT) single crystal and epoxy are fabricated for ultrasonic transducer applications by a modified dice-and-fill method. Excellent properties for ultrasonic transducer applications have been achieved, such as high electromechanical coupling coefficient (kt=73%), lower acoustic impedance (Z=16MRayl) and moderate dielectric constant. Based on this lead-free piezoelectric single crystal composite, single-element ultrasonic transducer and linear array have been fabricated and characterized. Both types of transducers exhibit similar performance with broad bandwidth of exceeding 100%. The promising results show that these lead-free composites have the potential to be used for high-performance ultrasonic transducers.

Design and fabrication of a high frequency annular array for medical ultrasound systems

Most high frequency (>15MHz) medical ultrasound systems are based on single element transducers mechanically scanned. These systems can provide images with excellent resolution. However, single element transducers are often limited by the fixed focal point and small depth of field. High frequency medical ultrasound annular arrays consisting of concentric rings of elements are focused electronically. These arrays are desirable to avoid the fixed focal point of the single element transducers and improve the depth of field. This paper demonstrate an over 10MHz annular array transducer with novel piezoelectric single crystal. This transducer exhibits good energy conversion performance with a very low insertion loss at the center frequency. The transducer is promising for intravascular ultrasonic imaging and other applications. This work was supported by the National Natural Science Foundation of China (Grant Nos. 10904093 and 61031003), the Science and Technology Grant Scheme funds from Shenzhen Government (No. 08CXY-23).

Piezoelectric Materials Used in Underwater Acoustic Transducers

Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and single crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.

Development of a pressure sensor using a piezoelectric material thin film

In this paper, we show the process of research and development of a combustion pressure sensor using an aluminum nitride (AlN) thin film, which we developed for the first time in the world. At the time we envisaged the R&D in 2003, most sensors used a piezoelectric single crystal. The research of a combustion pressure sensor using an AlN thin film was an unexplored field, and the usefulness of an AlN thin film was not yet well recognized. However, since we started the R&D, domestic and foreign auto parts companies and universities showed interest, and we carried out joint research with a domestic company and a university toward practical use of the sensor. Consequently, we have succeeded in developing a sensor of small size, high sensitivity, and without the need of cooling. We now conduct research to resolve the problems such as stabilization of sensor signals and simplification of the sensor structure for practical use.

Effects of Copper Oxide Doping on the Properties of Sodium Potassium Niobate (Na0.5K0.5) NbO3 Piezoelectric Single Crystals Grown by Flux Method

 Abstract—Lead free piezoelectric single crystals of sodium potassium niobate (K0.5Na0.5)NbO3 and 0.5wt%, 1wt%, 1.5wt% of copper oxide CuO doped sodium potassium niobate (K0.5Na0.5)NbO3 (KNN) single crystals were grown by high- temperature solution method and the dielectric properties, morphology and domain pattern were investigated. The flux used during crystal growth is eutectic mixture of potassium carbonate K2CO3 and sodium carbonate Na2CO3. Additions of small amounts of boron oxide B2O3 further lower the melting temperature of the eutectic mixture. It was found that 1.5wt% CuO doped single crystals of sodium potassium niobate exhibits excellent dielectric properties. XRD results showed sharp peaks indicating good crystalline behavior of both pure and CuO doped KNN crystals. Phase analysis showed that all samples crystallized in pure orthorhombic perovskite phase. A slight decrease in the diffraction angles has been observed with increase in doping concentration. This is due to the replacement of Nb5+ ions by Cu2+ ions, leading to the formation of higher oxygen vacancies with the doping concentrations.

Characterization of a high-power piezoelectric energy-scavenging device based on PMN-PT piezoelectric single crystals

In this paper, we present the calculations and the results for vibration-energy-scavenging performances based on a piezoelectric single-crystal beam. Using the measured mechanical damping ratio and electro-mechanical coupling coefficient of a novel cantilever structure device, we calculated the output performances and compared them with the measured results. A device based on a bimorph cantilever structure with a proof mass was designed to have a natural resonance frequency of about 60 Hz, and the energy-scavenging capability of piezoelectric single crystal was measured. The results showed that several tens of AC volts and a few milliwatts power were achieved under a 0.1 grms vibration condition. Also using this device and a commercial power management circuit, we performed Li-ion battery charging experiment.

Growth and electrical properties of 0.95Na0.5Bi0.5TiO3–0.05K0.5Bi0.5TiO3 lead-free piezoelectric crystal by the TSSG method

0.95Na0.5Bi0.5TiO3–0.05K0.5Bi0.5TiO3 lead-free piezoelectric single crystal with rhombohedral structure was grown by the top-seeded solution growth method. The temperature dependence of dielectric constant and loss, polarization hysteresis loops, the optimum poling condition and the electromechanical coupling property were investigated for the 〈100〉-oriented as-grown crystal. The curves ε(T) show two anomalies, which are related to the two phase transformations at the temperature range of 130–340°C. The piezoelectric constant d33 and electromechanical coupling coefficient kt for the 〈001〉-oriented crystal at room temperature reached 147pC/N and 0.52, respectively. The value of kt demonstrated a relatively stable thermal electromechanical coupling property over the temperature range of 15–130°C.

Anisotropy of Lamb and SH waves propagation in langasite single crystal plates under the influence of dc electric field

Paper is presented the results of computer simulation. Effect of the homogeneous dc electric field influence on the propagation of zero and first order Lamb and SH waves in piezoelectric langasite single crystal plates for a lot of cuts and directions have been calculated. Crystalline directions and cuts with maximal and minimal influence of dc electric field have indicated. Effect of hybridization of plate modes has been discussed.

Correlation between dielectric properties and chemical composition of the tourmaline single crystals

Dielectric responses were studied on piezoelectric tourmaline single crystals of widely varying chemical composition from different geological origins. The dielectric constants at constants stress, and dissipation factor were measured as a function of frequency (100-1000 kHz) using method of substitution. A correlation between two independent dielectric constants (along and perpendicular to crystallographic c-axis) is observed, and dependence of dielectric constants on chemical composition is presented.

Magnetoelectric Sensors With Directly Integrated Charge Sensitive Readout Circuit—Improved Field Sensitivity and Signal-to-Noise Ratio

The large magnetoelectric (ME) coupling in the ME laminates makes them attractive for ultrasensitive room temperature magnetic sensors. Here ,we investigate the field sensitivity and signal-to-noise ratio (SNR) of ME laminates, consisting of magnetostrictive and piezoelectric layers (Metglas and piezopolymer PVDF were used as the model system), which are directly integrated with a low noise readout circuit. Both the theoretical analysis and experimental results show that increasing the number of piezoelectric layers can improve the SNR, especially at low frequencies. We also introduce a figure of merit to measure the overall influence of the piezolayer properties on the SNR and show that the newly developed piezoelectric single crystals of PMN-PT and PZN-PT have the promise to achieve a very high SNR and consequently ultra-high sensitivity room temperature magnetic sensors. The results show that the ME coefficients used in early ME composites development works may not be relevant to the SNR. The results also show that enhancing the magnetostrictive coefficient, for example, by employing the flux concentration effect, can lead to enhanced SNR.

（企業研究フロンティア講演）セメント部会-硫酸塩土壌に建築された住宅基礎コンクリートの劣化現象

（企業研究フロンティア講演）セメント部会-硫酸塩土壌に建築された住宅基礎コンクリートの劣化現象

Characterization of piezocrystals for practical configurations with temperature- and pressure-dependent electrical impedance spectroscopy

Piezoelectric single crystal materials such as (x)Pb(Mg(1/3)Nb(2/3))O(3-)(1-x)PbTiO(3) (PMN-PT) have, by some measures, significantly better performance than established piezoelectric ceramics for ultrasound applications. However, they are also subject to phase transitions affecting their behavior at temperatures and pressures encountered in underwater sonar and actuator applications and in non-destructive testing at elevated temperatures. Materials with modified compositions to reduce these problems are now under development, but application-oriented characterization techniques need further attention. Characterization with temperature variation has been reported extensively, but the range of parameters measured is often limited and the effects of pressure variation have received almost no attention. Furthermore, variation in properties between samples is now rarely reported. The focus of this paper is an experimental system set up with commercially available equipment and software to carry out characterization of piezoelectric single crystals with variation in temperature, pressure, and electrical bias fields found in typical practical use. We illustrate its use with data from bulk thickness-mode PMN-29%PT samples, demonstrating variation among nominally identical samples and showing not only the commonly reported changes in permittivity with temperature for bulk material but also significant and complicated changes with pressure and bias field and additional ultrasonic modes which are attributed to material phase changes. The insight this provides may allow the transducer engineer to accelerate new material adoption in devices.