Poling Method Research Articles

Achieving high piezoelectric performance in Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric single crystals through pulse poling technique

To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals.

Impact of the Hydrophilicity of Poly(sarcosine) on Poly(ethylene glycol) (PEG) for the Suppression of Anti-PEG Antibody Binding.

A method of poly(ethylene glycol) (PEG) conjugation is known as PEGylation, which has been employed to deliver therapeutic drugs, proteins, or nanoparticles by considering the intrinsic non- or very low immunogenic property of PEG. However, PEG has its weaknesses, and one major concern is the potential immunogenicity of PEGylated proteins. Because of its hydrophilicity, poly(sarcosine) (P(Sar)) may be an attractive-and superior-substitute for PEG. In the present study, we designed a double hydrophilic diblock copolymer, methoxy-PEG-b-P(Sar) m (m = 5-55) (mPEG-P(Sar) m ), and synthesized a triblock copolymer with hydrophobic poly(l-isoleucine) (P(Ile)). We validated that double hydrophilic mPEG-P(Sar) block copolymers suppressed the specific binding of three monoclonal anti-PEG antibodies (anti-PEG mAbs) to PEG. The results of our indirect ELISAs indicate that P(Sar) significantly helps to reduce the binding of anti-PEG mAbs to PEG. Importantly, the steady suppression of this binding was made possible, in part, thanks to the maximum number of sarcosine units in the triblock copolymer, as evidenced by sandwich ELISA and biolayer interferometry assay (BLI): the intrinsic hydrophilicity of P(Sar) had a clear supportive effect on PEG. Finally, because we used P(Ile) as a hydrophobic block, PEG-P(Sar) might be an attractive alternative to PEG in the search for protein shields that minimize the immunogenicity of PEGylated proteins.

GEAR-RACK TOOL FOR GENERATING AN INVOLUTE FLANK. VIRTUAL POLE METHOD

In the paper, an approach to the issue of gear-rack type tool profiling is proposed, based on the “virtual pole” method. The proposed issue has also been solved based on complementary fundamental theorems, but the virtual pole method has the advantage of a simplified form of writing the generating movements. This makes it possible to avoid the need to write the relative movements between the tool and the piece.The paper presents the application of the virtual pole method for generating an involute profile.

VIRTUAL POLE METHOD - ALTERNATIVE METHOD FOR PROFILING RACK TOOLS

This paper presents a variant for determining the enwrapping condition, in the case of rack gear type tools. This variant was called the “virtual pole method”. The position of the virtual pole Pv is defined by the movement angle of the blank together with the centrode associated with the generated profile. The virtual pole method allows translating in the centrodes’ absolute movements, a point on the generated profile, on to the rack tool profile, thus determining the geometric locus representing the generating tool profile. The new method is easier to apply, while remaining scientifically rigorous. By applying the proposed algorithm, it is no longer necessary to write explicitly the relative movements between the tool and the piece, which simplifies the calculation process and eliminates some of the possibilities for errors.

Electrical Stimulations Generated by P(VDF-TrFE) Films Enhance Adhesion Forces and Odontogenic Differentiation of Dental Pulp Stem Cells (DPSCs).

Biophysical and biochemical cues of biomaterials can regulate cell behaviors. Dental pulp stem cells (DPSCs) in pulp tissues can differentiate to odontoblast-like cells and secrete reparative dentin to form a barrier to protect the underlying pulp tissues and enable complete pulp healing. Promotion of the odontogenic differentiation of DPSCs is essential for dentin regeneration. The effects of the surface potentials of biomaterials on the adhesion and odontogenic differentiation of DPSCs remain unclear. Here, poly(vinylidene fluoride-trifluoro ethylene) (P(VDF-TrFE)) films with different surface potentials were prepared by the spin-coating technique and the contact poling method. The cytoskeletal organization of DPSCs grown on P(VDF-TrFE) films was studied by immunofluorescence staining. Using atomic force microscopy (AFM), the lateral detachment forces of DPSCs from P(VDF-TrFE) films were quantified. The effects of electrical stimulation generated from P(VDF-TrFE) films on odontogenic differentiation of DPSCs were evaluated in vitro and in vivo. The unpolarized, positively polarized, and negatively polarized films had surface potentials of -52.9, +902.4, and -502.2 mV, respectively. DPSCs on both negatively and positively polarized P(VDF-TrFE) films had larger cell areas and length-to-width ratios than those on the unpolarized films (P < 0.05). During the detachment of DPSCs from P(VDF-TrFE) films, the average magnitudes of the maximum detachment forces were 29.4, 72.1, and 53.9 nN for unpolarized, positively polarized, and negatively polarized groups, respectively (P < 0.05). The polarized films enhanced the mineralization activities and increased the expression levels of the odontogenic-related proteins of DPSCs compared to the unpolarized films (P < 0.05). The extracellular signal-regulated kinase (ERK) signaling pathway was involved in the odontogenic differentiation of DPSCs as induced by surface charge. In vivo, the polarized P(VDF-TrFE) films enhanced adhesion of DPSCs and promoted the odontogenic differentiation of DPSCs by electrical stimulation, demonstrating a potential application of electroactive biomaterials for reparative dentin formation in direct pulp capping.

Castor‐oil derived polyurethane/barium titanate piezoelectric smart composite coatings for energy harvesting applications: Prediction and experimental characterization of electro‐elastic properties

AbstractSustainable and environment‐friendly polymer composite smart paints/coatings with polyurethane (PU) derived from castor‐oil (CO) as the matrix and barium titanate (BTO) microparticles as piezo‐active inclusions (2, 4, 6, 8, and 10 vol.%) have been prepared employing ultrasonication and solvent casting, followed by contact DC poling method. Relative dielectric constants varied from 5.26 ± 0.37 for pristine COPU to 8.9 ± 0.36 for COPU/10 vol.% BTO composite, at a frequency of 1 kHz. Piezoelectric strain constant d33 of the poled films varied from 0.0 pC/N for pristine castor‐oil based polyurethane (COPU) to 1.2 pC/N for COPU/10 vol.% BTO (CPBT‐5) composite. Tensile tests showed that the elastic modulus varied from 1.98 ± 0.003 MPa for pristine COPU to 5.13 ± 0.02 MPa for COPU/10 vol.% BTO composite. Dynamic mechanical analysis confirmed the viscoelastic nature of the smart paints. Measurement of current–voltage response under different compressive loads indicates that COPU/10 vol.% BTO composite can generate a current of ~28 nA and voltage of ~8 V under a dynamic compressive load of 40 N, applied at a frequency of 1 Hz. These experiments were complemented by Fourier transform infra‐red spectroscopy and scanning electron microscopy. In addition, finite element analyses based on periodic boundary conditions have been performed to predict the effective electro‐elastic properties of these piezoelectric smart composite coatings.Highlights Castor‐oil‐based PU piezoelectric composites with BTO inclusions were developed. Increase in BTO content up to 10 vol.% increases dielectric constant by ~1.7 times. COPU/BTO composites exhibit significantly increased piezoelectric response. Elastic and viscoelastic properties are also enhanced with increasing BTO content. Finite element models show a good match with experimental results.

Analysis of heavy metals in Ictalurus punctatus (channel catfish), Perca flavescens (yellow perch), and Aplodinotus grunniens (freshwater drum) in a Coastal Lake Michigan Watershed

Studies on metals in Great Lakes fish have focused typically on mercury (Hg), with less attention on other contaminants. Few studies exist on fish from drowned river mouths supplying the Great Lakes. This paper reports on metals in 3 common species, Ictalurus punctatus (channel catfish), Perca flavescens (yellow perch), and Aplodinotus grunniens (freshwater drum, a.k.a. sheep head) sampled from a coastal lake in West Michigan, USA. 135 fish were taken with pole and line methods from 6 different locations from July 2019–July 2021. Flank tissues were processed and analyzed by ICP-OES techniques for antimony (Sb), arsenic (As), barium (Ba), cadmium (Cd), cerium (Ce), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), nickel (Ni), selenium (Se), and zinc (Zn). Eight metals detected at quantifiable levels were Ba, Cr, Cu, Fe, Mg, Mn, Se, and Zn. Mg levels were the highest for all sites and all fish, with averages ranging from 300-1400 ppm (mg/kg of wet tissue). Zn concentrations ranged 11–21 ppm, Fe 4–14 ppm, Se 1–5 ppm, Mn about 0.4–1 ppm, and Cu below 1 ppm. Cr was only quantifiable in 34 % of the fish at <1 ppm, and Ba was detectable in 20 % of the fish, from approximately 0.1 to 4 ppm. Results were examined for statistically-significant differences between species and sites. Comparison of 3 species from one site showed sheep head had lower levels of all metals, except Fe, which were indistinguishable from perch. Cu was higher in catfish than perch, and Mn and Ba concentrations were lower in sheep head by 10× and 100×, respectively, when compared to other species. Zn, Mg, Fe, and Mn concentrations were different in perch from different sites; and, sheep head contained different concentrations of Se, Zn, Fe, Mn, Cr, Cu, and Ba between sites.

Piezoelectric PVDF‐TrFE nanocomposite mats filled with BaTiO3 nanofibers: The effect of poling conditions

AbstractBaTiO3 nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF‐TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β‐crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two‐step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d33 (−31.7 pC N−1), strongly dependent on the added BaTiO3 nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices.

Maksillada İki Farklı Ogmentasyon Tekniğinin Karşılaştırılması: Olgu Sunumu

Aim: &#x0D; Dental implant applications are most common treatment methods for rehabilitation of edentulous jaws. The severe bone deficiency could not be allowed implant therapies. Various augmentation methods could be used for reconsruction. In this case report tent-pole and onlay grafting techniques were performed in case at edentulous maxilla with radiological evaluation at 6 months follow-up.&#x0D; Materials and Methods:&#x0D; CBCT (Cone beam computed tomography) were obtained from patient. Extraction of all teeth and explantation of 2 implants were planned because of periodontal problems. The ramus onlay grafting was decided to apply for both anterior side of the maxilla and tent pole technique for right premolar area of maxilla.&#x0D; Results:&#x0D; It was observed 3.5 mm horizontal bone gain at the right maxillary anterior side, 4.8 mm horizontal bone gain at the left maxillary anterior side and 3.4 mm horizontal and 6.8 mm vertical bone gain at right premolar side after 6 months.&#x0D; Conclusion:&#x0D; Tent pole and onlay grafting methods are successful treatment options for alveolar ridge augmentation. Nevertheless, autografts could not be enough in every case. In this situation, xenografts and allografts applications with tent pole technique could be preferred as an effective method for alveolar ridge augmentation both horizontally and vertically.

A one-step process for multi-gradient wettability modification on a polymer surface.

The surface modification technique is applied in microfluidic devices to modify wettability and achieve different flow velocities. Currently available methods for poly(dimethylsiloxane) (PDMS) surfaces may reliably induce wettability changes, but only one area can be altered at a time. This work introduces the controlled gradient oxygen plasma modification (CGPM) technique, which layers several resin masks with varying porosities on top of the PDMS surface. Selective wettability of the PDMS surface can be achieved by varying the oxygen plasma density above the modified material's surface by manipulation of the porosity value. Through the implementation of the COMSOL plasma module, the impact of the mask's porosity, through-hole size, distribution, and distance from the PDMS surface on wettability was studied. The suggested CGPM approach was characterized by contact angle measurements. During the 25-second CGPM procedure, the PDMS surface's contact angle continually changed from 8.77° to 76.98°. An integrated microfluidic device was created and manufactured to identify D-dimers to illustrate this method. In comparison with standard oxygen plasma treatment, the D-dimer assay was finished in 10 minutes and had a dynamic range of 1-1000 ng mL-1, with a peak fluorescence signal augmentation of 78.3% and an average fluorescence intensity enhancement of 31.1%.

Multimaterial Topology Optimization Method of Surface-Mounted PMSM Rotor Poles Based on Variable Density Representation

Multimaterial Topology Optimization Method of Surface-Mounted PMSM Rotor Poles Based on Variable Density Representation

Constrained Series PI, PID and PIDA Controller Design Inspired by Ziegler–Nichols

Abstract The present paper complements the results of several recent papers on higher-order (HO) controllers with automatic-reset. A modification of the two-step tuning of the constrained second-order derivative controllers based on integrator-plus-dead-time (IPDT) models is proposed. In the first step, the linear controller is designed using the multiple real dominant poles (MRDPs) method to avoid the slowdown of the closed-loop dynamics due to the presence of slow poles. In the second step, the smallest time constant of the numerator of the MRDP-optimal controller transfer function is selected as the automatic-reset time constant. The derived control method was tested on a thermal system for the filament disc dryer to demonstrate the deployment, tuning, use and impact of controllers with increasing derivative degree in practical applications. It is shown that the use of HO controllers is similar to the traditional hyper-reset controllers (i.e. series proportional-integral-derivative [PID] controllers) from the user’s point of view. However, the advantages are faster transient responses while maintaining sufficiently smooth input and output shapes of the process with a minimum number of monotonic intervals. The overall design can be seen as a generalisation and discretisation of the Ziegler and Nichols graphical tuning method. One of the main new features is the consideration of a constrained control signal, as is typical for a pulse width modulated (PWM) actuator. Such actuators are often used in speed-controlled electric drives and in power electronics, among other applications.

Application of Quasi-Fractional Order PI Controller to IPDT Plant Control

The paper focuses on the design of a fractional order PI controller (FO-PI) and the verification of the properties of the control loop with an integral plus dead time (IPDT) system. The fractional order integrator in the controller is approximated by the Oustaloup method. The multiple dominant pole method (MDPM) is used to tune the controller parameters. The input parameters for controller tuning are obtained by optimization using the algorithm presented in the paper. The properties of the control loop with the FO-PI controller tuned in this way have been verified by simulation and compared with the properties of the control loop using an integer order PI controller.

Design and performance of ultra-broadband composite meta-absorber in the 200Hz-20kHz range

In this study, a composite meta-absorber with a flexible size is proposed, and a genetic algorithm is used to optimize the geometric dimensions under normal incidence and free field conditions. With an overall thickness of 0.2 m, the quasi-perfect sound absorption is achieved in the 200 Hz - 20 kHz range. The sound pressure and sound intensity distributions inside the composite meta-absorber prove the incident sound wave is effectively localized inside the structure. Comparing the effective sound velocities in layers 1 and 10 with the sound velocity in air, it is possible to infer that the slow sound phenomenon is more pronounced at the bottom of THE composite meta-absorber, due to the different combinations of lateral plates and cavities. The coupling relationship between internal loss and radiation loss of the meta-absorber was revealed using the zero and pole method, proving the ultra-broadband and quasi-perfect sound absorption characteristics. Tests of the sound absorption coefficient in impedance tubes and reverberation chambers confirm the effective broadband sound absorption performance. The composite meta-absorber in this study can be directly used to reduce broadband noise. Moreover, it also provides ideas for the design of sound-absorbing metamaterials.

Predatory Responses and Feeding Behaviour of Three Elasmobranch Species in an Aquarium Setting

Many progressive aquariums worldwide house various elasmobranch species as part of their commitment to conservation awareness and the long-term well-being of these creatures. These aquariums face the challenge of enabling these natural predators to live harmoniously with other fish without triggering natural predation. This research, conducted at Zoomarine Algarve in Southern Portugal, aimed to investigate the behaviour of three elasmobranch species (Carcharhinus melanopterus (1:1:0), Triaenodon obesus (1:0:0), and Pteroplatytrygon violacea (0:3:0)) when exposed to different feeding mechanisms. The goal was to provide them with opportunities for alternative predatory behaviours beyond their typical feeding techniques and to reduce the likelihood of natural predation. The study took place under controlled conditions within a community habitat. Four feeding methods (pole, short buoy, long buoy, and PVC) were tested during morning, afternoon, and evening periods, using five different prey species. The results shed light on which feeding method aligns best with each species’ distinct physiological standards and predatory tendencies and revealed their prey preferences. All three species interacted with all feeding methods, with P. violacea showing a strong preference for the pole method. T. obesus favoured bony fish, while C. melanopterus showed a preference for cephalopods. P. violacea interacted with all prey types but displayed no marked preference. These various feeding methods and prey options also function as environmental enrichment strategies, enhancing the complexity of the habitat and providing the animals with more choices and control, ultimately promoting their welfare in captivity.

The convenient method and application for monitoring the health of traffic sign poles based on mobile phone

Traffic sign poles are crucial components of the highway system, and their maintenance mainly relies on the subjective judgment of staff, which is low-efficiency and will lead to mistaken inspections. This paper proposes a convenient and effective method to monitor the health of sign poles by using a mobile phone. It is unknown whether a mobile phone can be used as a conventional acceleration sensor. Therefore, the performance of the mobile phone was initially tested to ensure its suitability for acquiring the acceleration data of the traffic sign pole. The results show that the acceleration sensor of mobile phones is high-performance and can be used as a traditional acceleration sensor under the similar sampling frequency. The mobile phone can measure the 1st, 2nd and 5th natural frequencies of the traffic sign pole. Although the 1st and 5th natural frequencies have a large error with simulation, the 2nd natural frequency is accurate and stable. The looseness of the base connection greatly impacts on the 2nd natural frequency, which can be used as a measure of the loose base connection. The 2nd natural frequency was measured for 21 times and found to conform to a normal distribution. The relationship between the 2nd natural frequency and base connection loosening was investigated, which fitted to the equation. The fitting result is good and can be used to predict the degree of sign pole base connection loosening. Therefore, the mobile phone based convenient health monitoring method for traffic sign poles is feasible.

Promoted osteogenesis by corona discharge poling induced in electroactive piezoelectric bioceramics

Rapid bone reconstruction and regeneration process is still a problem to be solved in the clinical orthopedic treatment. In vivo electric stimulation (ES) shows great promise in repair and regeneration of damaged tissues, and the piezoelectric characteristic of nature bone tissue make the electrical activity piezoelectricity biomaterials feasible and attractive in bone regeneration. Herein, we prepared a biocompatible lead-free piezoelectric ceramic K0.5Na0.5NbO3 (KNN) via solid phase sintering, which possesses wireless ES capability through corona discharge poling. Compared with the traditional piezoelectric ceramic polarization methods, corona discharge poling is a non-contact and biologically safer electrical poling method without electrodes or insulating liquids. The results of piezoelectricity, the water contact angle, the protein adsorption, surface potential characteristics of KNN ceramics and bone mesenchymal stem cells (BMSCs) behavior on ceramics, showed that after corona discharge poling the surface of KNN piezoelectric ceramic became hydrophilic, and positively charged, and the electrostatic effect formed by these charges promoted protein adsorption and BMSCs attachment and proliferation, which further promoted osteogenic differentiation. In conclusion, we used the corona discharge to polarize KNN piezoelectric ceramics and excellent biocompatibility of the ceramics was maintained after poling. Meanwhile, our work demonstrated the potential application of piezoelectric bio-ceramic materials in bone regeneration.

Parametrization and Optimal Tuning of Constrained Series PIDA Controller for IPDT Models

The new modular approach to constrained control of higher-order processes with dominant first-order dynamics using generalized controllers with automatic resets (ARCs) is addressed. The controller design is based on the multiple real dominant pole (MRDP) method for the integrator plus dead time (IPDT) process models. The controller output constraints are taken into account by inserting the smallest numerator time constant of the controller transfer function into the positive feedback loop representing the automatic reset (integral) term. In the series realization of the proportional–integral–derivative–acceleration (PIDA) controller (and other controllers with even derivative degree), the time constant mentioned is complex, so only the real part of the time constant has been used so far. Other possible conversions of a complex number to a real number, such as the absolute value (modulus), can be covered by introducing a tuning parameter that modifies the calculated real time constant and generalizes the mentioned conversion when designing controllers with constraints. In this article, the impact of the tuning parameter on the overall dynamics of the control loop is studied by simulation. In addition, an evaluation of the stability of the closed-loop control system is performed using the circle criterion in the frequency domain. The analysis has shown that the approximation of the complex zero by its real part and modulus leads to a near optimal response to the set point tracking. The disturbance rejection can be significantly improved by increasing the tuning parameter by nearly 50%. In general, the tuning parameter can be used to find a compromise between servo and regulatory control. The robustness and applicability of the proposed controller is evaluated using a time-delayed process with first-order dominant dynamics when the actual transfer function is much more complicated than the IPDT model. A comparison of the proposed MRDP-PIDA controller with series PI, PID and PIDA controllers based on a modified SIMC method has shown that the MRDP-PIDA controller performs better than the SIMC method, although the SIMC uses a more complex process model.

Micrometeorological Analysis and Glacier Ablation Simulation in East Kunlun

Worldwide, there are great challenges for meteorological monitoring and glacier ablation monitoring in high-altitude mountain areas. It is often difficult to capture fine-scale climate and glacial changes in high-altitude mountainous areas due to the harsh natural environment and the extreme lack of observational sites. Based on high-altitude meteorological stations erected on the eastern shore of Aqikkule Lake (AQK) and at the terminus of Shenshechuan Glacier (SSG), as well as on mass balance data from SSG, the characteristics and correlation of temperature, solar radiation, relative humidity, precipitation, wind speed and direction of the two regions, and the mass balance in the ablation area of SSG from 30 May 2022 to 18 May 2023 were analyzed, and the average melting depth of SSG was simulated. The results indicate the following: (1) The average annual temperature of AQK and the terminus of SSG is −3.7 °C and −7.7 °C, respectively, and the vertical lapse rate of temperature in the summer half of the year is greater than that in the winter half of the year. Precipitation timing has a great influence on daily temperature differences. (2) Precipitation in both places is concentrated in summer; the glaciers in this area are of the summer recharge type, and precipitation has a significant reducing effect on the solar incident radiation and increases the relative humidity in this region. (3) AQK and SSG both have local circulation development, in the area of AQK all year round due to the lake effect, while the terminus of SSG only has the development of valley winds in the summer, being controlled in the winter by the westerly wind belt. (4) The average mass balance value of the ablation area of SSG was −1786 mm as measured by the range poles method. The average annual ablation depth of SSG simulated by using the empirical formula was 587–597 mm, which is not large compared with other glacier areas in the Tibetan Plateau, and it has the characteristics of typical continental-type glaciers.

Microstructure observation of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals by scanning electron microscopy

Piezoelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals (SCs) prepared by the Bridgman method on plates of 0.3 mm thickness were polarized by six different poling methods and their piezoelectric properties were analyzed. The sine wave AC-poled PMN-PT SC showed the best properties: a piezoelectric constant d 33 of 1920 pC N−1 and a free dielectric permittivity of 8050 without any spurious mode vibration. The plates were then broken to observe their microstructures by scanning electron microscopy. Clearly different vertical stripe and horizontal stripe microstructures were observed in the vertical direction of SCs. The differences in SC microstructures on the fracture surface were found to depend on the direction in which compressive and tensile stresses were applied. These results suggest that special attention should be paid when discussing the correlation between piezoelectric properties and SC microstructure, since the structure of piezoelectric SCs can vary depending on the sample geometry and pretreatment method.