Piezoelectric Constant D15 Research Articles

Modeling, analysis and validation of a novel asymmetric cruciform harvester with d15 mode

d31 mode piezoelectric property has been widely used in vibration-based energy harvester, however there are very few studies on fully utilizing maximum piezoelectric constant d15. In this study, a novel asymmetric cruciform harvester with d15 mode is proposed. The asymmetric cruciform beam is composed of one main beam and two asymmetric side beams. Under one directional excitation, the torsional vibration of the proposed harvester is easily induced by the asymmetry of side beams and added masses. A mathematical model of bending-torsional coupling is established and then verified by finite element method and experiments. The results indicate that, compared with the reference harvester with equal total mass, the resonant frequency of the proposed harvester can be significantly reduced. Furthermore, its output power can be highly enhanced. Based on the established theoretical model, the effects of design variables (side beam length, added mass thickness, and piezoelectric position) on performances (resonant frequency and output power) are analyzed in detail. The analytical results illustrate that the proposed harvester can output higher power at lower frequencies by increasing its asymmetry. The asymmetry can be enlarged by increasing the difference in added masses and length of the two side beams. More importantly, the proposed harvester can effectively reduce the performance deviations caused by piezoelectric position, which is beneficial to fabrication and applications.

Orientation Dependence of Elastic and Piezoelectric Properties in Rhombohedral BiFeO₃.

Through a coordinate transformation approach, crystal orientation dependences of elastic and piezoelectric properties at room temperature have been investigated in a three-dimensional space for rhombohedral bismuth ferrite (BiFeO3). Elastic constants (stiffnesses) c11′, c12′, c13′ and piezoelectric constants d15′, d31′, d33′ along arbitrary orientations were obtained based on crystalline asymmetry characteristics of 3m point group BiFeO3. Parameters along specific orientations obtaining the largest values were presented. The max c11′ = 213 × 109 N/m2 could be achieved in planes with = 0° and 90°. The max c12′ = c13′ = 132.2 × 109 N/m2 could be achieved along directions at θ = 13° and θ = 77° inside three mirror planes, respectively. The max d15′ = 27.6 × 10−12 C/N and the max d31′ = 12.67 × 10−12 C/N could be both obtained along directions at θ = 69° inside mirror planes. The max d33′ = 18 × 10−12 C/N could be obtained at θ = 0°, along the spontaneous polarization axis. By adopting optimal directions, the elastic and piezoelectric parameters of BiFeO3 could be significantly enhanced which shows applications for the growth of BeFeO3 films with preferred orientations and enhanced properties.

A novel thickness polarized d15 shear piezoelectric fiber composites

As smart materials, piezoelectric ceramics played an important role in actuation, sensing, structural health monitoring and vibration damping systems. This letter reports a novel structure of shear piezoelectric fiber composites (SPFC), which was polarized in the thickness direction, and drived on the transverse direction with interdigitated electrodes. Under a driving condition of 270V at 0.1Hz, a fixed SPFC showed a shear strain of 176.5ppm and a Mylar membrane cantilever beam structure exhibited a tip displacement of 0.343mm, corresponding to an effective piezoelectric constant d15 of 400pm/V. These results provide a novel idea for the SPFC applied in actuation and vibration control areas.

Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 °C. Measured free dielectric constants and were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS.

Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy.

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 °C. Measured free dielectric constants and were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS.

Active twist control methodology for vibration reduction of a helicopter with dissimilarrotor system

In this work, an active vibration reduction of hingeless composite rotor blades withdissimilarity is investigated using the active twist concept and the optimal control theory.The induced shear strain on the actuation mechanism by the piezoelectric constantd15 from the PZN–8% PT-based single-crystal material is used to achieve more active twistingto suppress the extra vibrations. The optimal control algorithm is based on theminimization of an objective function comprised of quadratic functions of vibratory hubloads and voltage control harmonics. The blade-to-blade dissimilarity is modeled using thestiffness degradation of composite blades. The optimal controller is applied tovarious possible dissimilarities arising from different damage patterns of compositeblades. The governing equations of motion are derived using Hamilton’s principle.The effects of composite materials and smart actuators are incorporated into thecomprehensive aeroelastic analysis system. Numerical results showing the impact ofaddressing the blade dissimilarities on hub vibrations and voltage inputs requiredto suppress the vibrations are demonstrated. It is observed that all vibratoryshear forces are reduced considerably and the major harmonics of moments arereduced significantly. However, the controller needs further improvement to suppress1/rev moment loads. A mechanism to achieve vibration reduction for the dissimilar rotor systemhas also been identified.

Temperature dependence of transverse and shear mode properties for 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal with the optimal orientation

The temperature dependence of the coupling constants kμν and piezoelectric constants dμν, gμν of transverse and shear mode 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN–29%PT) single crystals with optimal orientation from room temperature to 115 °C were reported. From 20 °C to approximately 80 °C, k31 increases slightly from 91.0% to 93.5%, while d31 increases from 1900.0 to 4500.0 pC N−1. When the temperature exceeds 80 °C, both k31 and d31 begin to drop. Similarly, the coupling factor k15 increases from 95% to 97%, while the piezoelectric constant d15 increases from 4769.4 to 14293.2 pC N−1when the temperature rises from room temperature to 93 °C. When the temperature goes beyond 93 °C, the shear-mode piezoelectric properties start to decay. We also study the temperature dependence of the elastic compliances and , both of which show strong dependence of the temperature. The service temperature for PMN–29%PT is determined to be lower than 80 °C for transverse vibration and lower than 93 °C for shear-mode samples. These would effectively guide the correlative device designs and practical applications.

2 T domain-engineered piezoelectric single crystals: Calculations and application to PZN–12%PT poled along [101

This work is devoted to a study of the [101] domain-engineered PZN–12%PT single crystals. The full electromechanical tensor of PZN–12%PT in its tetragonal single domain state 1T is determined by the resonance method and used as input data. Observations of the domain structure of the [101]-poled 2T crystals by polarized light microscopy reveal a laminar structure consisting of thin layers stacked along the macroscopic polarization direction. We give analytical expressions for effective constants of this laminate multidomain pattern, taking into account the clamping effect resulting from domain coexistence. The calculated effective properties are found in good agreement with the experiments within experimental uncertainties. It is found that domain coexistence affects primarily the transverse dielectric constants ε11 and ε22. This effect is related to the emergence of internal shear stresses and depolarizing electric fields that are most significantly driven by the shear piezoelectric constant d15 and dielectric anisotropy ε11T−ε33T of the single domain state.

Pressure dependence of piezoelectric properties of aPb(Mg1/3Nb2/3)O3–PbTiO3 binary system single crystal near a morphotropic phase boundary

The piezoelectric properties of aPb[(Mg1/3Nb2/3)0.68]Ti0.32O3 binary system single crystal poled along the [001] direction in therhombohedral phase were investigated under pressures up to 400 MPa at25 °C. For the transverse electromechanical property, the differenceΔf between the resonancefr and antiresonancefrequencies fa, the Δf/fr and the electromechanical coupling coefficientk31 value in thek31 mode withhydrostatic pressure (p) became smaller because of the increase infr and the almostconstant fa with p. The k31 value decreased by 16% at 400 MPa. On the other hand, for the longitudinal electromechanical property,the Δf, theΔf/fr and thek33 valuein the k33 mode with p remained almost constant because of the almost constantfr and fa with p. The changes in the values of the elastic compliancess11E ands33E withp were found to be largefrom the changes in fr and fa with p. s11E ands33E at 400 MPa wereestimated to be 35.4 and 75.1 × 10−12 m2 N−1, respectively. A mechanical quality factorQ almost constantwith p in thek33 mode in contrast tothe large decrease in Q in the k31 mode with p in the pressure range up to 200 MPa was observed. Ak33 value almostconstant with p is considered, on the basis of the engineered domain concept, to bedue to the stable domain configuration responsible for the longitudinalk33 mode. Furthermore, the superior piezoelectric properties of the rhombohedral [001]single crystal in the vicinity of the morphotropic phase boundary compositionwere recently pointed out to come from the large shear piezoelectric constantd15 of their single domain property. The hydrostatic pressure cannot influence thepiezoelectric properties from the viewpoint of the contribution of the large shear moded15, since the uniform pressure introduces no shearing stresses. Consequently, thek33 value measured forthe k33 mode remainedalmost constant with p in the measured pressure range.

Single-domain properties of 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 single crystals under electric field bias

We report a complete set of material properties of single-domain, relaxor-based 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 [PMN–33%PT] single crystals. Because the single-domain state is unstable in natural conditions, a bias electric field of 0.2 MV/m was applied along the dipole direction of the rhombohedral phase during the measurements. It was found that the electromechanical coupling coefficient k33 and the piezoelectric constant d33 for single-domain PMN–33%PT are 69% and 190 pC/N, respectively. Both of them are much smaller than those of multidomain PMN–33%PT poled along [001] direction. However, the shear piezoelectric constant d15 of single-domain PMN–33%PT reaches 4100 pC/N, which is much higher than that of multidomain PMN–33%PT.

Active Torsional Vibration Control Experiments Using Shear-Type Piezoceramic Sensors and Actuators

In this article, active control of pure torsional vibrations using piezoelectric shear-type transducers is discussed Pure torsional vibrations can be sensed and controlled by incor porating these transducers into tube-type structures. The effects of changing the electrode orientation with respect to the polarization direction of the shear mode transducers is discussed. Two types of shear mode piezoelectric transducers-ring-type with tangential polarization and shell-type with axial polarization-are examined. In other words, the piezoelectric constant d15 is utilized. Different sizes of phenolic and pyrex tubes are employed in this experiment Since the sensor signal is proportional to the rate of change of the angular displacement, a velocity feedback control technique is ap plied. The time domain responses for the first mode, and fre quency domain responses for the first three modes, are demon strated. Individual and simultaneous control for the first three fundamental modes, respectively, have been successfully obtained.

Ferroelectric properties of tungsten bronze lead barium niobate (PBN) single crystals

Abstract A ferroelectric tungsten bronze single crystal of Pb0.33Ba0.70Nb2O6 was grown from a melt using the Czochralski technique. The crystal belongs to the tetragonal point group 4mm with the spontaneous polarization parallel to the ‘c’ axis. The room temperature lattice parameters were a = 12.50 A and c = 3.995 A. The spontaneous polarization was found to be 0.40 C/m2°C. The Curie transition was 350°C as determined from the temperature dependence of the dielectric constants. The pyroelectric properties were found to be typical of other tetragonal ferroelectric bronzes. Dielectric constant ϵ11 and piezoelectric constant d15 show a strong enhancement from the approach of the tetragonal:orthorhombic morphotropic phase boundary and it is clear that crystals with composition in the tetragonal phase field closer to this boundary will be of major interest for piezoelectric and electro-optic applications.