Berlincourt Method Research Articles

Negative Capacitance and Intrinsic Ferroelectric Behavior in α-MoO3 Culminating as a Robust Piezoelectric Energy Harvester

Driven by the notion that the spectrum of ferroelectric applications can be widened and the current subset of materials could be replaced with earth-abundant, lead-free materials, single-phase α-MoO3 (MO) with biaxial van der Waals gap was synthesized, revealing an orthorhombic Pmcn symmetry with a layered ABAB... sequence, with mirrored A and B layers. The force-driven dielectric constant of MO was found to be 12.5 at 0.5 N force level, which showed dielectric saturation behavior with increasing dynamic force. Ferroelectric studies revealed a maximum of 46% efficiency at 10 kV/cm external electric field, and piezoelectric modulus (d33) of 30 pC/N was obtained using the Berlincourt method. Negative capacitance (NC) effects were observed and attributed to the ferroelectric-induced emf and the inductive reactance, in accordance with Lenz’s law. Based on the confluence of the aforementioned features, a piezoelectric energy harvester (PEH) was fabricated, which reached a peak voltage of 4 V under repetitive finger tapping. The power density of the PEH under 100 MΩ resistive load was found to be 7.32 × 10–1 μW/cm2. This enshrines MO as a promising piezoelectric candidate with exotic properties that can be tailored to have multifaceted applications in the realm of sensing and energy harvesting to drive Internet-of-Things and Industry 4.0.

In Situ Synchrotron XRD Characterization of Piezoelectric Al1−xScxN Thin Films for MEMS Applications

Aluminum scandium nitride (Al1-xScxN) film has drawn considerable attention owing to its enhanced piezoelectric response for micro-electromechanical system (MEMS) applications. Understanding the fundamentals of piezoelectricity would require a precise characterization of the piezoelectric coefficient, which is also crucial for MEMS device design. In this study, we proposed an in situ method based on a synchrotron X-ray diffraction (XRD) system to characterize the longitudinal piezoelectric constant d33 of Al1-xScxN film. The measurement results quantitatively demonstrated the piezoelectric effect of Al1-xScxN films by lattice spacing variation upon applied external voltage. The as-extracted d33 had a reasonable accuracy compared with the conventional high over-tone bulk acoustic resonators (HBAR) devices and Berlincourt methods. It was also found that the substrate clamping effect, leading to underestimation of d33 from in situ synchrotron XRD measurement while overestimation using Berlincourt method, should be thoroughly corrected in the data extraction process. The d33 of AlN and Al0.9Sc0.1N obtained by synchronous XRD method were 4.76 pC/N and 7.79 pC/N, respectively, matching well with traditional HBAR and Berlincourt methods. Our findings prove the in situ synchrotron XRD measurement as an effective method for precise piezoelectric coefficient d33 characterization.

Dual-Ring Method: Lateral Piezoelectric Coefficient (e31,f) Measurement on Unstructured Thin Films

In the literature, measurement of piezoelectric properties is often absent in work describing the processing of these materials. For a measurement to be used in process development and control, it should preferably be performed shortly after the process itself. However, there are only a few methods available to characterize the piezoelectric constants on an unstructured thin film. Furthermore, these methods do not measure the lateral piezoelectric coefficient e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31,f</sub> , although it is the most important piezoelectric parameter for many devices. In this article a new method is introduced to enable the measurement of the lateral piezoelectric coefficient on unstructured wafers. For the measurement, the entire wafer is bent. The charge generated by the wafer bending is used to calculate the piezoelectric constant. An analytical formula is derived to establish the relation between geometry, substrate properties, the force and the charge. This formula is compared with finite element analyses (FEA). FEA is used to investigate the impact of geometric variations on the measurement. The method is evaluated on sputtered aluminum nitride and shows good correlation with the 4-point bending method. As the output signal of the new method is some magnitudes higher compared to the well-known Berlincourt method. The requirements on the measurement equipment are much less stringent, resulting in the need for only few basic tools that are accessible to researchers without access to specialized laboratories.

Modular lead-free piezoceramic/polymer composites with locally adjustable piezoelectric properties

Lead-free piezoceramics are gaining interest in the field of bone tissue engineering due to their surface charges and improved bone cell adhesion. However, monolithic materials are less suitable for more complex medical conditions, as the properties must be tailored and locally adaptable. Therefore, we designed a modular composite of ceramic building blocks and polymer-matrix to customize the piezoelectric properties with individual polarization of each block, while maintaining the benefits of each phase. Barium titanate building blocks were prepared by injection molding and were assembled into 2-2-layered and modular structures, which were bonded with barium titanate-filled (ΦP = 35 vol %) epoxy resin. The piezoelectric response was determined using direct excitation via Berlincourt method, and the influence of the matrix thickness as well as the different polarization orientations of individual building blocks was investigated.

Relation between Structure, Mechanical and Piezoelectric Properties in Cellular Ceramic Auxetic and Honeycomb Structures

Optimizing renewable energy harvesting is of major importance in the following decades. In order to increase performance and efficiency, an ideal balance of mechanical and piezoelectric properties must be targeted. For this purpose, the approach of ceramic auxetic and honeycomb structures made of (Ba,Ca)(Zr,Ti)O3 (BCZT) which is produced via injection molding is considered. The main design parameter is the structural angle θ which is varied between −35° and 35°. Its effect on compressive strength, Young's modulus, and Poisson's ratio are determined via uniaxial compression tests and digital image correlation (DIC). Maximum compressive strength of 95 MPa at 0° (porosity of 59%) is found, which is superior to conventional porous ceramics of the same porosity. The piezoelectric constants d33 (max. 296 pC N−1) and g33 (max. 0.068 Vm N−1) are measured via the Berlincourt method and also exceed expectations, regardless of the structure. The theoretical models of Gibson and Ashby (mechanical) and Okazaki (piezoelectrical), as well as finite element method simulations, strengthen and explain the experimental results.

Ultra-high piezoresponse in tantalum doped potassium sodium niobate single crystal

Ferroelectric materials reveal an ultra-high piezoelectric effect because of their spontaneous polarization and show high potential for applications. At present, the lead-free piezoelectric materials are in a great demand because of their environmentally friendly character, but their performance needs to be improved. Generally, in order to enhance the piezoelectric coefficients, researchers could rely on a phase boundary and/or to grow single crystals. Here, a Ta-doped (K, Na)NbO3 (KNN) single crystal with the orthorhombic–tetragonal (O–T) phase boundary is grown via the top-seed solution growth method. Excellent piezoelectric coefficients (d33 ≈ 560 pC/N via the Berlincourt method and d33* ≈ 1353 pm/V derived from strain-electric field loops) are achieved in a K0.40Na0.60Ta0.41Nb0.59O3 single crystal. What is more, with the electric field rising from 0.5 kV/cm to 4 kV/cm, the converse d33 and the strain hysteresis level improve from 580 pm/V to 640 pm/V and from 0.052 to 0.104, respectively. Our results clarify that the high d33 can be attributed to the high domain density and the labyrinthine-domain structure. In addition, the electric-field-induced phase transition is also observed, which is supposed to cause the high d33*. This work not only reports the ultra-high piezoresponse of the KNN-based single crystal but also provides strong evidence for its mesoscale origin.

The influence on sintering and properties of sodium niobate (NaNbO3) ceramics by “non-stoichiometric” precursor compositions

Abstract NaNbO3 powders from different processing routes and various near equimolar concentrations of metal ions were sintered to ceramics and investigated concerning their structural and electric properties. The particle sizes obtained from two different conventional solid state reactions and one solvent – based route were in the range of 40 nm - 10 μm and the variation of precursor composition covered 48–52 mol% Na. Sintering temperatures were defined by the deviation from the equimolar composition between 950 and 1375 °C, which is due to the coexistence of second phases Na3NbO4, Na2Nb4O11 and NaNb3O8. Small particle sizes (40 nm–3 μm) on deviation from equimolar composition resulted in higher relative densities at lower sintering temperatures. The coexistence of second phases influences structural and electric characteristics. The former were investigated by X-ray Diffraction (XRD) for phase analysis, Scanning Electron Microscopy (SEM) for defining grain sizes and Energy-Dispersive X-ray (EDX) spectroscopy for deciding the elemental composition. The impact on electrical conductivity and dielectric properties are examined by impedance spectroscopy and the resulting d33 coefficients of 15–29 pC/N are measured by Berlincourt method.

The direct piezoelectric effect in the globular protein lysozyme

Here, we present experimental evidence of the direct piezoelectric effect in the globular protein, lysozyme. Piezoelectric materials are employed in many actuating and sensing applications because they can convert mechanical energy into electrical energy and vice versa. Although originally studied in inorganic materials, several biological materials including amino acids and bone, also exhibit piezoelectricity. The exact mechanisms supporting biological piezoelectricity are not known, nor is it known whether biological piezoelectricity conforms strictly to the criteria of classical piezoelectricity. The observation of piezoelectricity in protein crystals presented here links biological piezoelectricity with the classical theory of piezoelectricity. We quantify the direct piezoelectric effect in monoclinic and tetragonal aggregate films of lysozyme using conventional techniques based on the Berlincourt Method. The largest piezoelectric effect measured in a crystalline aggregate film of lysozyme was approximately 6.5 pC N−1. These findings raise fundamental questions as to the possible physiological significance of piezoelectricity in lysozyme and the potential for technical applications.

Low-cost (0.1BiYbO3-0.9PbTiO3)-PbZrO3-xMn high Curie temperature piezoelectric ceramics with improved high-temperature performance

Here, we report the structure and performance of a low-cost high Curie temperature (TC) Mn-doped ternary BiYbO3-Pb(Zr,Ti)O3 (BY-PZT-xMn) perovskite piezoelectric ceramic system. The partial substitution of Mn for the A-site Pb, B-site Ti and Zr of the ternary system enhanced both the piezoelectric coefficient and the mechanical quality factor, indicating that the variable valence element induced combinatory soft and hard doped characteristics. The improved electrical performance was found to be related to the improved density and homogeneity, and a correlation between the piezoelectricity and the grain size was also observed. More importantly, a Mn doping level of less than 0.8 mol. % also obviously enhanced the thermal stability of the samples, as reflected by the higher TC and depolarization temperature (Td) measured via both in situ Berlincourt method and annealing experiments, and a correlation between TC and tetragonality of BY-PZT-xMn system was observed. The sample with 0.8 mol. % Mn showed a remarkable overall performance with a d33 of 246 pC/N and a TC around 400 °C, which is expected to be promising for high temperature piezoelectric device applications.

Substrate-Free Thick-Film Lead Zirconate Titanate (PZT) Performance Measurement Using Berlincourt Method

Lead Zirconate Titanate or PZT is a high performance piezoelectric material which is able to generate charges when a proportional amount of stress is applied on the material. It has the potential to be used to fabricate micro-power generator for powering low power electronic devices, on top of already existence sensors and actuators. One of the indicators for comparing the performance of the smart materials is the piezoelectric charge coefficient, d33. In this paper, the actual d33 of PZT fabricated in the form of substrate-free thick-films were measured using Berlincourt Method whereby a standard dynamic force is applied to the materials and the resultant value of charges is recorded and compared over a period of time after the thick-films were polarized. The d33 values are compared between substrate-based and substrate-free specimens show a difference of about 45 % as a result of clamping effect contributed by d31. The experiment results also show that the thick-film PZT processed at 950 °C and polarized at 220 V with a thickness of about 120 μm has a piezoelectric charge coefficient of 82 pC/N.

Structure and electrical properties of (1−x)(0.1BiYbO3–0.9PbTiO3)–xPb(Zn1/3Nb2/3)O3 high-temperature ternary piezoelectric ceramics

The microstructure and electrical properties of a new ternary high temperature piezoelectric ceramic system (1−x)(0.1BiYbO3–0.9PbTiO3)–xPb(Zn1/3Nb2/3)O3 (BYPT–PZN, x=0.05–0.5) were reported. The ternary system had a perovskite main phase with a tetragonal symmetry. With increasing PZN content, the tetragonality decreased, and interestingly, both the piezoelectric properties and mechanical quality factor of the samples were largely improved. Microstructural characteristics indicated that the improved piezoelectric performance was also due to the improved density, structural stability and homogeneity. The sample with 40mol% of PZN (x=0.4) showed the optimum piezoelectric response and a Tc of around 400°C. However, direct high temperature d33 measurement via the Berlincourt method indicated that depolarization in the sample did not occur up to 350°C.

Comprehensive investigation of elastic and electrical properties of Li/Ta-modified (K,Na)NbO3 lead-free piezoceramics

A full set of elastic and electrical coefficients of (K,Na)NbO3-based lead-free piezoceramics with a nominal composition of Li0.03(K0.48Na0.52)0.97(Nb0.8Ta0.2)O3 (abbreviated as KNNLT) was evaluated by the standard resonance method, and compared to those of K4CuNb8O23 doped (K0.45Na0.55)NbO3 (KNN-KCN) as well as typical Pb(Zr,Ti)O3-based piezoceramics PZT5A. The measurement of intermediate elastic stiffness and compliance coefficients of KNNLT indicated that KNNLT is elastically “softer” than KNN-KCN but “harder” than PZT5A. An extremely high piezoelectric stiffness coefficient h33 = 68.8 × 108 V/m was obtained, due to an especially low clamped dielectric constant ε33S of 361. And a large longitudinal electromechanical coupling factor k33 = 57% was observed in the KNNLT system. Furthermore, the piezoelectric coefficient d33 of KNNLT was characterized via three distinctive methods: the resonance method, the Berlincourt method, and the converse piezoelectric strain measurement; while these three techniques yielded values of 174 pC/N, 195 pC/N, and 308 pm/V, respectively. The difference in d33 values determined by the three methods may be attributed to different measurement frequencies and extrinsic piezoelectric contributions related to domain wall vibration and domain switching. Besides, the piezoelectric performances of KNNLT piezoceramics were found insensitive to frequency but susceptible to temperature and electric field cycling.

A Capacitance-Based Methodology for the Estimation of Piezoelectric Coefficients of Poled Piezoelectric Materials

A methodology is proposed to estimate the piezoelectric coefficients of bulk piezoelectric materials using simple capacitance measurements. The extracted values of d 33 and d 31 from the capacitance measurements were 506 pC/N and 247 pC/N, respectively. The d 33 value is in agreement with that obtained from the Berlincourt method, which gave a d 33 value of 500 pC/N. In addition, the d 31 value is in agreement with the value obtained from the optical method, which gave a d 31 value of 223 pC/V. These results suggest that the proposed method is a viable way to quickly estimate piezoelectric coefficients of bulk unclamped samples.

Comparative measurements of piezoelectric coefficient of PZT films by berlincourt, interferometer, and vibrometer methods

Chemical solution deposition (CSD) techniques were used to prepare lead zirconate (Zr) titanate (Ti) (PZT) thin films with Zr/Ti ratios of 30/70 and 52/48. Usually CSD processing is restricted to making crack-free, single-layer films of 70-nm thick, but modifications to the sol-gel process have permitted the fabrication of dense, crack-free, single layers up to 200 to 300 nm thick, which can be built-up into layers up to 3-microm thick. Thicker PZT films (> 2-microm single layer) can be produced by using a composite sol-gel/ceramic process. Knowledge of the electroactive properties of these materials is essential for modeling and design of novel micro-electromechanical systems (MEMS) devices, but accurate measurement of these properties is by no means straightforward. A novel, double-beam, common-path laser interferometer has been developed to measure the longitudinal (d33) piezoelectric coefficient in films; the results were compared with the values obtained by Berlin-court and laser scanning vibrometer methods. It was found that, for thin-film samples, the d(33,f) values obtained from the Berlincourt method are usually larger: than those obtained from the interferometer and the vibrometer methods; the reasons for this are discussed.

Piezoelectric PZT films for MEMS and their characterization by interferometry

Piezoelectric films can be used in micro-electromechanical system (MEMS) devices because the piezoelectric effect can provide high forces with relatively low energy losses. The energy output by a piezoelectric film per unit area is proportional to the film thickness, so it is desirable to have relatively thick films. Chemical solution deposition (CSD) techniques were used to prepare lead zirconate titanate (PZT) thin films with Zr/Ti ratios of 30/70 and 52/48. Usually CSD processing is restricted to making crack-free single layer films of ca 70 nm thick, but modifications to the sol-gel process have permitted the fabrication of dense, crack-free single layers up to 200-300 nm thick, which can be built-up into layers up to 3 μm thick. Thicker PZT films (>2 μm single layer) can be produced by using a composite sol-gel/ceramic process. Knowledge of the electro-active properties of these materials is essential for modeling and design of novel MEMS devices and accurate measurement of these properties is by no means straightforward. A novel double beam common path laser interferometer has been developed to measure the piezoelectric coefficient in films and the results were compared with the values obtained by Berlincourt method. A laser scanning vibrometer was also used to measuring the longitudinal (d 33 ) and transverse (d 31 ) piezoelectric coefficients for PZT films and ceramics and the results were compared to those obtained by the other methods. It was found that for thin film samples, the d 33,f values obtained from the Belincourt method is usually larger than those obtained from the interferometer method but smaller than those from the vibrometer method and the reasons for this are discussed.

Measurement of piezoelectric coefficients of lead zirconate titanate thin films by strain-monitoring pneumatic loading method

A method to simultaneously measure the longitudinal (d33) and transverse (d31) piezoelectric coefficients of a lead zirconate titanate (PZT) thin film was developed. This system was based on the pneumatic loading method but was modified to monitor the radial strain when a pressurized gas was introduced into the chamber. The results of the bulk piezoelectric material measured by this system coincided with that measured by both the Berlincourt method and the resonance method. The effective d33 and the real d31 of the PZT thin film fabricated by the sol-gel multiple coating method, and poled at 300 kV/cm were 125 and −60 pC/N, respectively. The real d33 estimated upon considering the constraints by the silicon substrate was 180 pC/N.

Longitudinal piezoelectric coefficient measurement for bulk ceramics and thin films using pneumatic pressure rig

A pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge. It was found that the stress state imposed included components both perpendicular and parallel to the film plane. The later were due to friction and could largely be relieved through sliding of the O-rings to their equilibrium positions for a given pressure. The induced charge stabilized as equilibrium was reached and most of it was produced by the normal component of the stress. By minimizing the surface friction and compensating for the remnant in-plane stress, very good agreement was obtained among the d33 values measured by the Berlincourt method, double-beam interferometry and this method for a bulk lead zirconate titanate (PZT) sample. The d33 value of PZT thin films made by sol-gel processing was also measured. The as deposited films usually showed very weak piezoelectricity with d33 values ranging from 0 to 10 pC/N, indicating little pre-existing alignment of the domains. With increasing poling field, the d33 value also increased and saturated at poling fields exceeding three times the coercive field. Typically, films with thicknesses around 1 μm had d33 values of 100 pC/N. Good agreement between double-beam interferometry and this technique was also obtained for thin films. The small difference between the two measurements is attributed to the effect of mechanical boundary conditions on the effective d33 coefficient.