High Mechanical Quality Factor Research Articles

A hollow cylindrical linear nut-type ultrasonic motor

A hollow, linear, nut-type, ultrasonic motor based on two degenerate, 3 rd -order bending modes in the section plane of cylinders is presented in this paper. The stator and rotor of the motor are both cylindrical and hollow, making the motor appropriate for applications where a light path, electric wire or optic fiber is required to pass through the motor. A new structure with four PZT plates bonded on the stator is proposed here. and the other had all eight sides bonded with PZT plates. The results show that the new design with four PZT plates has a higher mechanical quality factor, vibrates with larger amplitude, and has comparable performance to the stator with eight PZT plates. The motor with four PZT plates reached an upward speed of 0.95 mm/s when the load force was 3 g, and the maximum thrust force was 0.35 N. DOI: http://dx.doi.org/10.5755/j01.mech.22.6.13366

Characterization of acceptor-doped (Ba, Ca)TiO3 “hard” piezoelectric ceramics for high-power applications

Acceptor Mn or Co-doped Ba0.925Ca0.075TiO3 (abbreviated as BCT-Mn and BCT-Co) lead-free piezoelectric ceramics with high density and fine grains were synthesized by conventional solid-state reaction method. The phase structure and electrical properties of the ceramics were investigated. The acceptor-doped BCT ceramics were found to exhibit asymmetrical polarization-electric field hysteresis loops corresponding to the presence of an internal bias field Ei, indicating that the domain walls were pinned by preferentially oriented defect dipoles formed by the acceptors and oxygen vacancies. High mechanical quality factor Qm and low dielectric loss tanδ were obtained for the ceramics due to the strong internal bias field (Ei =4–5kV/cm). In particular, BCT-Mn ceramics exhibited the best properties, with mechanical quality factor Qm =1020, dielectric loss tanδ=0.2% and piezoelectric coefficient d33 =190 pC/N. Furthermore, the planar electromechanical coupling factor kp for BCT-Mn ceramics was found to be larger than 0.4 in the temperature range of 25°C to 75°C. These results indicate that the Mn-doped BCT lead-free ceramics material is a promising candidate for high-power piezoelectric applications.

Hybrid confinement of optical and mechanical modes in a bullseye optomechanical resonator.

Optomechanical cavities have proven to be an exceptional tool to explore fundamental and applied aspects of the interaction between mechanical and optical waves. Here we demonstrate a novel optomechanical cavity based on a disk with a radial mechanical bandgap. This design confines light and mechanical waves through distinct physical mechanisms which allows for independent control of the mechanical and optical properties. Simulations foresee an optomechanical coupling rate g0 reaching 2π × 100 kHz for mechanical frequencies around 5 GHz as well as anchor loss suppression of 60 dB. Our device design is not limited by unique material properties and could be easily adapted to allow for large optomechanical coupling and high mechanical quality factors with other promising materials. Finally, our devices were fabricated in a commercial silicon photonics facility, demonstrating g0/2π = 23 kHz for mechanical modes with frequencies around 2 GHz and mechanical Q-factors as high as 2300 at room temperature, also showing that our approach can be easily scalable and useful as a new platform for multimode optomechanics.

Effects of acceptor doping on sintering and piezoelectric properties of (K0.4825Na0.4825Li0.035)(Nb0.8Ta0.2)O3 lead-free piezoelectric ceramics

The effects of the doping of three cations with different valence states (Cu2+, Ga3+ and Ge4+) on the sintering and electrical properties of (K0.4825Na0.4825Li0.035)(Nb0.8Ta0.2)O3 (KNLNT) ceramics have been investigated in detail. The results show that these three cations all act as acceptor dopant and improve the sintering of the KNLNT ceramics; ceramic samples with excellent properties can be obtained at much lower sintering temperatures, and the range of useable sintering temperatures has been widened. In addition, the acceptor doping with Cu2+, Ga3+ and Ge4+ has resulted in increases in the Curie temperatures and improvements in ferroelectric properties. The results also show that for the KNLNT ceramics, in order to obtain high mechanical quality factor (Qm), the divalent cation Cu2+ can be used, resulting in a three-fold enhancement in Qm. In contrast, in order to obtain a high planer electromechanical coupling factor (kp), the tetravalent cation Ge4+ can be utilized, and kp can be improved by as much as 54%.

Acoustic confinement in superlattice cavities

The large coupling rate between the acoustic and optical fields confined in GaAs/AlAs superlattice cavities makes them appealing systems for cavity optomechanics. We have developed a mathematical model based on the scattering matrix that allows the acoustic guided modes to be predicted in nano and micropillar superlattice cavities. We demonstrate here that the reflection at the surface boundary considerably modifies the acoustic quality factor and leads to significant confinement at the micropillar center. Our mathematical model also predicts unprecedented acoustic Fano resonances on nanopillars featuring small mode volumes and very high mechanical quality factors, making them attractive systems for optomechanical applications.

Magnetic resonance force detection using a membrane resonator

The availability of compact, low-cost magnetic resonance imaging instruments would further broaden the substantial impact of this technology. We report highly sensitive detection of magnetic resonance using low-stress silicon nitride (SiNx) membranes. We use these membranes as low-loss, high-frequency mechanical oscillators and find they are able to mechanically detect spin-dependent forces with high sensitivity enabling ultrasensitive magnetic resonance detection. The high force detection sensitivity stems from their high mechanical quality factor Q∼106[1,2] combined with the low mass of the resonator. We use this excellent mechanical force sensitivity to detect the electron spin magnetic resonance using a SiNx membrane as a force detector. The demonstrated force sensitivity at 300K is 4fN/Hz, indicating a potential low temperature (4K) sensitivity of 25aN/Hz. Given their sensitivity, robust construction, large surface area and low cost, SiNx membranes can potentially serve as the central component of a compact room-temperature ESR and NMR instrument having spatial resolution superior to conventional approaches.

A single-mode Mn-doped 0.27PIN-0.46PMN-0.27PT single-crystal ultrasonic motor

Mn-modified rhombohedral phase yPb(In1/2Nb1/2)O3-(1-x-y)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT:Mn) single crystal has attracted considerable attention for its outstanding piezoelectric properties and high mechanical quality factor. Here, we report a device innovation using Mn doped 0.27PIN-0.46PMN-0.27PT single crystal in a single-mode piezoelectric ultrasonic motor. Based on the analyses of actuator characteristics with finite element method, the PIN-PMN-PT:Mn crystal actuator predicts lower excitation frequency, lower driving voltage, and less power loss comparing with the PZT ceramic actuator. A prototype motor (size: 12 × 6 × 1.5 mm3) was fabricated and tested. The typical output of this PIN-PMN-PT:Mn motor is a speed up to 42.3 cm/s, a driving torque of 0.42 N cm, and an output power density of 0.45 W/cm3, under the driving voltage of 21 V0−P. This work presents that PIN-PMN-PT:Mn single crystal is quite advantageous in making miniaturized and high-power piezoelectric ultrasonic motors.

Laser cooling and control of excitations in superfluid helium

Superfluidity is a quantum state of matter that exists macroscopically in helium at low temperatures. The elementary excitations in superfluid helium have been probed with great success using techniques such as neutron and light scattering. However, measurements of phonon excitations have so far been limited to average thermodynamic properties or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of phonon excitations in real time. Furthermore, strong light–matter interactions allow both laser cooling and amplification. This represents a new tool to observe and control superfluid excitations that may provide insight into phonon–phonon interactions, quantized vortices and two-dimensional phenomena such as the Berezinskii–Kosterlitz–Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including the prospect of femtogram masses, high mechanical quality factors, strong phonon–phonon and phonon–vortex interactions, and self-assembly into complex geometries with sub-nanometre feature size. It takes extreme sensitivity to measure the elementary excitations in liquid helium-4. An optomechanical cavity with a thin film of superfluid inside can be used to both observe and control phonons in real time.

Effects of CuO doping on the piezoelectric properties of KNLNS–BZ ceramics

Lead-free piezoelectric ceramics with 0.96(K0.48Na0.52)0.95Li0.05Nb1−xSbxO3–0.04BaZrO3 (0.07 ≤ x ≤ 0.09) and 1 mol% CuO (KNLNSx–BZ–CuO) compositions were prepared with hard characteristics for possible application on piezoelectric transformers. The results showed that good piezoelectric properties were found for ceramics with x = 0.07 and 0.08 (d33, d31 and kp were similar for both compositions). The higher mechanical quality factor (Qm) corresponds to x = 0.07, which was close to 770. This combination of properties make the KNLNSx–BZ–CuO compositions promising materials for high power applications.

An approach to design and fabrication of resonant giant magnetostrictive transducer

The paper provides a comprehensive procedure for the mechanical and magnetic design of Langevin transducer based on giant magnetostrictive material. The the transducer is designed to work at its second mode of vibration, having high mechanical quality factor and low damping coefficient. The design procedure is based on an analytical model and it is verified by finite-element analysis. Experimental tests based on impedance response analysis in first and second modes are carried out on the prototype. Results confirm the appropriate design of this transducer, demonstrating the highest mechanical quality factor between the resonant transducers in the literature.

High-Temperature Piezoelectric Crystals for Acoustic Wave Sensor Applications.

In this review paper, nine different types of high-temperature piezoelectric crystals and their sensor applications are overviewed. The important materials' properties of these piezoelectric crystals including dielectric constant, elastic coefficients, piezoelectric coefficients, electromechanical coupling coefficients, and mechanical quality factor are discussed in detail. The determination methods of these physical properties are also presented. Moreover, the growth methods, structures, and properties of these piezoelectric crystals are summarized and compared. Of particular interest are langasite and oxyborate crystals, which exhibit no phase transitions prior to their melting points ∼ 1500 °C and possess high electrical resistivity, piezoelectric coefficients, and mechanical quality factor at ultrahigh temperature ( ∼ 1000 °C). Finally, some research results on surface acoustic wave (SAW) and bulk acoustic wave (BAW) sensors developed using this high-temperature piezoelectric crystals are discussed.

A MEMS PPA Based Active Vibration Isolator - STUDENT AWARD 3RD PLACE $500

Several types of micro-devices are adversely affected by high frequency mechanical vibrations present in the operating environment. Examples include MEMS vibratory gyroscopes and resonators, and micro-optics. Various types of MEMS vibration isolators have been developed for use in the packaging of these vibration sensitive devices. Passive isolators consist of a spring-mass-damper MEMS device and usually have a very high mechanical quality factor, which makes them susceptible to ringing at the isolator's resonant frequency. Active isolators have been realized by using state sensing of the proof mass motion and feeding one or more of these states back through an actuator to adjust the frequency response of the isolator. For example, the technique known as skyhook damping uses velocity feedback to adjust, and typically increase, the damping of the isolator. Although these technique are doable, they require state sensing or state estimation, with feedback electronics to drive the actuator. A simpler MEMS active vibration isolator architecture employs only a parallel plate actuator (PPA) with the MEMS spring-mass-damper structure. The PPA driven with a DC voltage, in its stable operating range, displaces the proof mass, which results in a change in the effective system spring constant due to the electrostatic spring softening effect. This results in a change in the resonant frequency and the quality factor of the isolator. However, due to the nonlinearities inherent in this type of device, the stable operating range is reduced as the PPA voltage is increased. Furthermore, even when the isolator is stable in steady-state, a sufficiently large transient response can also drive it into the unstable regime, resulting in the electrodes snapping into contact. In this study, the PPA based active vibrator isolator is developed and its performance is evaluated. The characteristics of the transient instability are investigated and its stable range of operation is specified, for booth external disturbances and rapid application of the control voltage. This MEMS PPA based active vibration isolator can improve performance compared to passive isolators, while being much simpler than state feedback active isolators.

Growth and enhanced electro-elastic properties of Nd3+: CNGS crystals with ordered langasite structure

In this letter, the Nd3+: Ca3NbGa3Si2O14 single crystals with high doping concentration (2at%) were grown using the Czochralski pulling method. For the first time, the dielectric, elastic and piezoelectric properties of Nd3+: CNGS crystals were evaluated at room temperature. The electro-elastic coefficients obtained for CNGS at room temperature crystals were given. It is proved that Nd3+: CNGS crystals have larger dielectric constants, piezoelectric constants and elastic compliance, as compared with those of CNGS crystals. Also, the new data were presented on the temperature dependence of electro-elastic properties from 25°C to 900°C. It is shown that Nd3+: CNGS crystals have a favorable temperature stability and high mechanical quality factor Q within the temperature range of 25–600°C.

Investigating the frequency spectrum of mechanical quality factor for piezoelectric materials based on phenomenological model

Heat generation due to losses restricts piezoelectric materials from maintaining a high power density, which will further limit the miniaturization of piezoelectric devices. As an evaluation index of the loss level, the mechanical quality factor shows an opposite tendency with losses. The mechanical quality factor should therefore be evaluated. By new methods to determine the mechanical quality factor, the highest mechanical quality factor has been discovered within the working bandwidth other than the resonance and antiresonance frequencies, which is almost double the value at the resonance. In this study, the prime determinant of the maximum value has been experimentally investigated on the basis of the phenomenological model of the admittance phase. The investigation experimentally infers that the change in the tendency of the phase leads to the appearance of the maximum value. Thus, the new phenomenon is experimentally explained for the first time.

High power density NaNbO3-LiTaO3 lead-free piezoelectric transformer in radial vibration modes

In the present work, the sintering temperature was able to substantially influence the microstructure and electrical properties of the lead-free ceramic 0.88NaNbO3–0.12LiTaO3. This composition without any acceptor doping presents a high mechanical quality factor, Qm, value of 1469 and a high Curie temperature of 305 °C by optimizing the sintering temperature at 1330 °C. We applied this material to make a device of disk-shaped piezoelectric transformers with a ring–dot structure and further focused on investigating the characteristics of the piezoelectric transformers. With matching load, a maximum efficiency of 92% occurs in the fundamental mode, and the maximum voltage gains are 5.5 and 3.7 for the fundamental and third radial vibration modes, respectively. The experimental results show a maximum output power of 10.5 W with a temperature rise of 27 °C. It is noteworthy that a high output power density (as high as 32.8 W cm−3) was obtained under a maximum input voltage of 180 V, which is comparable to the performance of PZT in a piezoelectric ceramic transformer device.

압전 PMN-PZT 단결정의 유전 및 압전 특성에 미치는 전극 종류의 영향

The effect of the electrode type on the dielectric and piezoelectric properties of Pb(Mg 1/3 Nb 2/3 )O₃-PbZrO₃-PbTiO₃ (PMN-PZT) single crystals was investigated in an effort to improve their properties for various piezoelectric applications. First, three different types of PMN-PZT single crystals [PMN-PZT-A (piezoelectrically soft type; dielectric constant ~ 10,000), PMN-PZT-B (piezoelectrically soft type; phase-transition temperature between the rhombohedral and tetragonal phases (T RT ) ~ 145℃), PMN-PZT-C (piezoelectrically hard type; high mechanical quality factor (Q m ) ~ 1,000)] were fabricated using the solid-state single crystal growth (SSCG) method. Then, four different types of electrodes [sputtered Au, sputtered Cr/Au, sputtered Ti/Au, and fired Ag] were formed on the single crystals, and their dielectric and piezoelectric properties were measured. The single crystals with a sputtered Ti/Au electrode showed the highest dielectric and piezoelectric constants but the lowest coercive electric field (E C ). The single crystals with a fired Ag electrode showed the lowest dielectric and piezoelectric constants but the highest coercive electric field (E C ). This dependence on the type of electrode was most significant in the piezoelectrically hard PMN-PZT-C single crystals. However, the effects of the electrode type on the phase transition temperatures (T C , T RT ) and dielectric loss were negligible. These results clearly demonstrate that it is important to select an appropriate electrode so as to maximize the dielectric and piezoelectric properties of single crystals in each type of piezoelectric application.

Tonpilz Underwater Acoustic Transducer Integrating Lead-free Piezoelectric Material

A Tonpilz transducer based on lead-free piezoelectric material was fabricated, modeled and characterized. The stack is composed of two rings of doped BaTiO3. This composition was initially chosen due to good electromechanical performance (kt at 40%) and high mechanical quality factor (Qm over 500). Comparison of the displacement at the center of the head mass was performed with a PZT-based Tonpilz with the same design for a center frequency at 22kHz.

Structure and electrical properties of (1 − x)(Na0.5Bi0.5)0.94Ba0.06TiO3–xSmAlO3 lead-free piezoelectric ceramics

(1 − x)(Na0.5Bi0.5)0.94Ba0.06TiO3–xSmAlO3 [(1 − x)BNBT6–xSA] lead-free piezoelectric ceramics were synthesized by conventional solid-state method. Effects of composition on the micro-structure and electrical properties of (1 − x)BNBT6–xSA ceramics were investigated. X-ray diffraction data shows that (1 − x)BNBT6–xSA ceramics form the pure perovskite phases, and the ceramics have the morphotropic phase boundary when x ≤ 0.0100. At room temperature, the electrical properties of the BNBT6 ceramics have been improved with the addition of appropriate SA. At room temperature, (1 − x)BNBT6–xBA ceramics at x = 0.0100 has the highest remnant polarization (P r = 47 μC/cm2), the highest piezoelectric coefficient (d 33 = 179 pC/N), the highest planar coupling factor (k p = 0.296), the higher dielectric constant (ɛ r = 1154) and higher mechanical quality factor (Q m = 131).

Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

Real-time DC-dynamic biasing method for switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators.

Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.