Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1997-12-08
2000-07-18
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
H01L 4108
Patent
active
060911832
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a piezoelectric element and a method for driving the same. In more details, the present invention relates to a piezoelectric element wherein piezoelectric properties such as a dielectric constant, a piezoelectric strain constant and a mechanical displacement caused by application of an electric field are less dependent on temperature and are excellent in resistance to temperature, and a method for driving the same, particularly to a piezoelectric element which is suitable for applying a high electric field, such as an ultrasonic vibrator, an ultrasonic inspector, a medical ultrasonic probe, a fish finder or a piezoelectric actuator, and a method for driving the same.
TECHNICAL BACKGROUND
Heretofore, a piezoelectric element has been used for an ignition element, an ultrasonic vibrator, an ultrasonic inspector, a medical ultrasonic probe, a fish finder, a frequency filter, an acoustic element, a piezoelectric actuator, or the like. The ultrasonic vibrator is a device which drives or vibrates a piezoelectric element by an electric field having a high frequency in an ultrasonic range, such as an ultrasonic motor or a washing vibrator.
The ultrasonic inspector transmits an ultrasonic vibration obtained in the same manner as the ultrasonic vibrator to a material to be inspected, such as an iron plate, to find defects such as cracks in the inspected material from information of echoes reflected back from the cracks.
By applying the same principle to organisms, the medical ultrasonic probe inspects tissues of humans.
The fish finder transmits an ultrasonic wave into water to search fish by using information reflected back from fishes.
The actuator accurately shows microscopic displacements in orders of micrometers or under micrometers by applying a voltage, and application to sounds like buzzers, precise control of a flow rate of a pump, a valve or the like, autotracking of a VTR head, autofocus, an equipment to accurately determine a placement of a mechanical cutting tool in a range of micrometers, an equipment for producing a semiconductor to determine a microscopic displacement, or the like, has been rapidly developed these days.
As a material for these piezoelectric elements, a PZT(PbZr.sub.x Ti.sub.y O.sub.3 :x+y=1,x.gtoreq.0,y.gtoreq.0)type material which contains lead, zirconium, titanium or the like and is an ABO.sub.3 type 25 perovskite compound having a divalent ion of lead or the like on the A site and a tetravalent ion of Zr, Ti or the like on the B site, is generally used. Specifically, a solid solution of the above PZT and a complex perovskite compound wherein the B site is on the average tetravalent, such as Pb(Ni.sub.1/2 W.sub.1/2)O.sub.3, Pb(Co.sub.1/3 Ni.sub.2/3)O.sub.3,Pb(Ni.sub.1/3 Nb.sub.2/3)O.sub.3 or the like, is already known.
The piezoelectric material is selected by searching a composition wherein a dielectric constant, an electromechanical coupling constant, a piezoelectric strain constant or a mechanical displacement caused by inducing an electric field is large.
It is clarified that the dielectric constant, the electromechanical coupling constant, the piezoelectric strain constant or the mechanical displacement caused by inducing an electric field generally indicates a maximum value when the above PZT type compound is in a state around a crystal phase boundary of a rhombohedral and a tetragonal (this is referred to as morphotropic phase boundary, and will be simply referred to as .left brkt-top.MPB.right brkt-bot. hereinafter), and the material is developed by searching the MPB.
For example, as a result of crystal phase identification by an X-ray diffraction measurement, it is crystallographically clarified that a crystal system of a pure PZT near room temperature is tetragonal when a ratio of constitutive elements on the B site of a perovskite structure, i.e. a molar ratio of Zr/Ti is at least 0/1 and is less than 0.53/0.47, that it is rhombohedral when Zr/Ti exceeds 0.53/0.47 and is at most 0.90/0.10, and that a crystal phase bound
REFERENCES:
patent: 4977547 (1990-12-01), Giniewicz et al.
patent: 5221872 (1993-06-01), Nishida et al.
patent: 5239518 (1993-08-01), Kazmar
patent: 5295487 (1994-03-01), Saitoh et al.
patent: 5729262 (1998-03-01), Akiyama et al.
Aihara Hitoshi
Akiba Takashi
Ichihara Takashi
Nishimura Tetsuhiko
Sato Junji
Budd Mark O.
Kasei Optonix Ltd.
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