Piezoelectric Bending Actuators Research Articles

Fabrication and high durability of functionally graded piezoelectric bendingactuators

A new type of functionally graded (FG) piezoelectric bending actuator wasproposed by the present authors in their former study and the advantage of thenew actuator over the traditional bimorph and unimorph actuators in internalstress distribution was illustrated by simulation results. In this study, thefabrication process of FG piezoelectric bending actuators is developed and thecharacteristics of the fabricated actuators are investigated. The materialcompositions with different dielectric and piezoelectric constants were selectedfrom the Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 family and used as the four layersin the new FG piezoelectric actuator. The piezoelectric constant and dielectricconstant were graded oppositely in the thickness direction. The durability of thefabricated FG piezoelectric actuators was measured in a vibration test andcompared with that of the traditional bimorph actuator to evaluate theimprovement of performance. The results show that the durability of the FGpiezoelectric actuators is much higher than that of the bimorph actuator.

High- Tc superconducting tunable filter with steep attenuation

We developed a compact RF receiver front-end subsystem using a high- T c superconducting sharp-skirt band-pass filter with a center frequency tuning function. The subsystem had two pairs of the tunable filter and an LNA on board. A 23-pole hairpin-type 2-GHz microstrip-line filter was fabricated with YBa 2Cu 3O y thin films deposited on a 35-mm-wide and 70-mm-long sapphire substrate. Attenuation characteristics were more than 40 dB at 1 MHz, apart from both the lower and the higher pass-band edges. For center frequency tuning, a 1-mm-thick dielectric sapphire plate was stacked on the filter, and the filtering characteristics were tuned by moving the plate using a piezoelectric bending actuator. The range of the center frequency modulation was more than 10 MHz with no significant degradation of the low-loss and sharp-skirt characteristics.

2 GHz tunable superconducting band-pass filter using a piezoelectric bender

We have developed a 2 GHz tunable superconducting band-pass filter using a piezoelectric bending actuator. The filter is a 12-pole microstrip line structure on 50 mm diameter LaAlO 3 substrate and has low loss and sharp skirt characteristics. The center frequency was 1.94 GHz and the attenuation characteristics were 30 dB at 1 and 3 MHz apart from the lower and higher band-edge, respectively. A sapphire (Al 2O 3) plate was stacked on the filter with an air gap and the gap thickness was controlled electrically from the outside of a refrigerator using a piezoelectric bending actuator. The center frequency of the filter could be adjusted within 11 MHz in such a manner that the low loss and sharp skirt characteristics were not degraded.

Basic investigations on a piezoelectric bending actuator for micro-electro-mechanical applications

This article deals with basic investigations into the development and manufacturing process of a piezoelectric animated micro actuator. The concept of the fabrication of a piezoelectric microactuator will be introduced and first fundamental investigations on materials characterization and process technology for the Pt bottom electrode and piezoelectric PZT layer will be presented. PZT thin film have been deposited with the chemical solution deposition (CSD) technique and have been characterized with dielectric and ferroelectric measurements. For optimization of actuator properties an analytical approach and a simulation with finite element method was carried out. This shows that the cantilever must have a length above 300 μm to reach a tip deflection higher than 10 μm at voltages comparable to those used in integrated circuits (IC). Additionally, stress measurements of each layer have been used to characterize the films mechanically.

K-2308 傾斜機能圧電アクチュエータに関する研究(J03-1 知的要素技術(1))(J03 知的材料・構造システム)

A new type of functionally graded (FG) piezoelectric bending actuator was proposed by the authors in former study and the advantage of the new actuator over the traditional bimorph and unimorph actuators in internal stress distribution was illustrated by simulation results. In this study, functionally graded piezoelectric bending actuator was designed and fabricated. The material compositions with different dielectric and piezoelectric constants were selected from the PNN-PZT family and used as the four layers in the new FG piezoelectric actuator. Durability of the fabricated FG piezoelectric actuators was measured in a vibration test and compared with that of the traditional bimorph actuator to evaluate the improvement of performance. The results showed that the durability of the FG piezoelectric actuators is much higher than that of the bimorph actuator.

A multilayer inplane bending piezoelectric actuator for dual-stage head-positioning control system

A novel multilayer in-plane bending piezoelectric actuator, called a multilayer split-morph, was designed and fabricated by thick-film screen-printing technology for a dual-stage head-positioning actuator system in a hard disk drive. The design, operation and theoretical principles have been described. The electromechanical performance of the fabricated actuators has been evaluated. The actuation stroke of the actuator is in inverse proportion to the thickness of the piezoelectric layer. The highest displacement/voltage sensitivity of 0.154µmV-1 is achieved in a trapezoidal multilayer split-morph with a thickness of 35 μm in each piezoelectric layer. The corresponding fundamental resonance frequency of the sway mode is high at 47 kHz in the trapezoid actuator with dimensions of 10.14 mm length, 3.08 mm and 1.54 mm widths of the two parallel sides of the trapezoid. The multilayer split-morph was designed to integrate directly onto a modified suspension load beam. With the combined attractive performances indicated above, the batch fabricated multilayer split-morph can provide a low-cost but promising solution for achieving very high track densities in a hard disk drive by implementing a high performance dual-stage head-positioning actuator system.

Electromechanical coupling and output efficiency of piezoelectric bending actuators

Electromechanical coupling mechanisms in piezoelectric bending actuators are discussed in this paper based on the constitutive equations of cantilever bimorph and unimorph actuators. Three actuator characteristic parameters, (e.g., electromechanical coupling coefficient, maximum energy transmission coefficient, and maximum mechanical output energy) are discussed for cantilever bimorph and unimorph actuators. In the case of the bimorph actuator, if the effect of the bonding layer is negligible, these parameters are directly related to the transverse coupling factor lest. In the case of the unimorph actuator, these parameters also depend on the Young's modulus and the thickness of the elastic layer. Maximum values for these parameters can be obtained by choosing proper thickness ratio and Young's modulus ratio of elastic and piezoelectric layers. Calculation results on four unimorph actuators indicate that the use of stiffer elastic material is preferred to increase electromechanical coupling and output mechanical energy in unimorph actuators.

Determination of Young’s modulus of the reduced layer of a piezoelectric RAINBOW actuator

The reduced and internally biased oxide wafer (RAINBOW) actuator, a new type of monolithic piezoelectric bending device, is composed of a reduced electromechanically passive layer and an unreduced piezoelectric layer. The determination of the elastic properties of the reduced layer is important for optimizing actuator performance. In this paper, an analytical expression for bending resonant frequency is derived for the cantilever RAINBOW actuator by using composite beam theory. A resonance method is then described for determining Young’s modulus of the reduced layer of RAINBOW actuator. As a piezoelectric bending actuator, RAINBOW can be excited by its electromechanically active PZT layer without using any external excitation method. Young’s modulus can be calculated by measuring its resonant frequency, sample geometry, and densities of component parts. For comparison, the Young’s modulus is also determined by measuring the resonant frequency of a completely reduced plate with an external acoustic excitation method. The results obtained by these two excitation methods show good agreement.

Monomorph Characteristics of Semiconductive Piezoceramics

New type piezoelectric bending actuators, monomorphs, originate basically from a metal- semiconductor contact (Schottky barrier) effect. This paper deals with a more sophisticated model, Metal-Insulator-Semiconductor (MIS) structure, to explain detailed monomorph characteristics. Furthermore, voltage versus current relation was measured on the actuator sample to obtain better understanding on the monomorph. The electric charge flow during half a voltage cycle is of the order of 2.6 C/m2, which is several times larger than the usual charge flow associated with the polarization reversal.