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Part: 7D-10-9000-2
Category:
Sensors
-> Piezoelectric Sensors
Description: Piezoelectric Ceramics Sensors
Company: Murata Manufacturing Co.
Datasheet: Download 7D-10-9000-2 datasheet File size : 137 kB
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P19E7.pdf 02.6.26
Piezoelectric Ceramic Sensors (PIEZOTITEr)
PIEZOELECTRIC CERAMICS SENSORS (PIEZOTITEr)
Murata Manufacturing Co., Ltd.
Cat.No.P19E-7
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This catalog has only typical specifications. Therefore, you are requested to approve our product specification or to transact the approval sheet for product specificaion before ordering.
P19E7.pdf 02.6.26
Preface
Recently, with the remarkable advance of electronics technology, various new products have come into existence. Until this time, the effect of electronics was seen most clearly in television, radio and other communications equipment, but as semiconductor technology, and computer technology advance, the range of electronics' effect on our lives has increased dramatically. In particular, sensor technology and the greater intelligent functions of today's microcomputers have served as a basis for the trend toward combining electronics and mechanics into what is called mechatronics. It is not merely the equipment itself, however, that has made all this possible. Within the equipment are highly sophisticated components with unique functions which can translate electrical to mechanical energy and mechanical to electrical energy and which play a large role in today's equipment modernization and advance. These are piezoelectric components. This catalog briefly introduces the basics of piezoelectric ceramics, Murata's piezoelectric ceramic materials, piezoelectric transducers and other products. Please insure the component is thoroughly evaluated in your application circuit. In case that the component is not mentioned in our statement, please contact your Murata representative for details.
!Note Please read rating and !CAUTION (for storage and operating, rating, soldering and mounting, handling) in this PDF catalog to prevent smoking and/or burning, etc.
This catalog has only typical specifications. Therefore, you are requested to approve our product specification or to transact the approval sheet for product specificaion before ordering.
P19E7.pdf 02.6.26
CONTENTS
PIEZOTITEr,CERAFILr and CERALOCKr in this catalog are the trademark of Murata Manufacturing Co., Ltd.
Preface
1 Introduction ----------------------------------------------------------------------------------------02 2 Characteristics of Piezoelectric Ceramics (PIEZOTITEr) ------03 1. Resonant Frequency and Vibration Mode .........03 2. Piezoelectric Material Constant Symbols ..........06 01 Frequency Constant N ........06 02 Piezoelectric Constants d and g ............06 03 Electromechanical Coupling Coefficient k ..........06 04 Mechanical Qm ........06 05 Young's Modulus Y ..07 06 Poisson's Ratio .....07 07 Density .......07 08 Relative Dielectric Constant ............07 09 Curie Temperature Tc .........07 10 Coercive Field Ec .....07
E E
T O
1 2 3 4 5
Introduction
Characteristics of Piezoelectric Ceramics (PIEZOTITEr)
Murata's Piezoelectric Ceramics (PIEZOTITEr) Material
Murata's Piezoelectric Ceramics Resonators (PIEZOTITEr)
Piezoelectric Ceramic (PIEZOTITEr) Applications
3 Murata's Piezoelectric Ceramics (PIEZOTITEr) Material ------08 1. Characteristics of Typical Materials .......08 2. Features of PIEZOTITEr Materials .........09 3. Temperature Characteristics and Aging ..09 4 Murata's Piezoelectric Ceramic Resonators (PIEZOTITEr) -------- 10 1. Shapes .......... 10 2. Standard Specification Models ............ 10 3. Notice ........... 11 5 Piezoelectric Ceramic (PIEZOTITEr) Applications ---- 12 Piezoelectric Actuator ... 13 Molded Underwater Transducer ..... 17 Ultrasonic Sensor ........ 18 Shock Sensor .... 26 Knocking Sensor Elements ..... 37 Ultrasonic Bubble Sensor ....... 38 Electric Potential Sensor ........ 39
!Note Please read rating and !CAUTION (for storage and operating, rating, soldering and mounting, handling) in this PDF catalog to prevent smoking and/or burning, etc.
This catalog has only typical specifications. Therefore, you are requested to approve our product specification or to transact the approval sheet for product specificaion before ordering.
P19E7.pdf 02.6.26
1 Introduction
1. What are Piezoelectric Ceramics?
Piezoelectric ceramics are known for what are called the piezoelectric and reverse piezoelectric effects. The piezoelectric effect causes a crystal to produce an electrical potential when it is subjected to mechanical vibration. In contrast, the reverse piezoelectric effect causes the crystal to produce vibration when it is placed in an electric field. Of piezoelectric materials, Rochelle salt and quartz have long been known as single-crystal piezoelectric substances. However, these substances have had a relatively limited application range chiefly because of the poor crystal stability of Rochelle salt and the limited degree of freedom in the characteristics of quartz. Later, barium titanate(BaTiO3), a piezoelectric ceramic, was introduced for applications in ultrasonic transducers, mainly for fish finders. More recently, a lead titanate, lead zirconate system(PbTiO3PbZrO3) appeared, which has electromechanical transformation efficiency and stability(including temperature characteristics)far superior to existing substances. It has dramatically broadened the application range of piezoelectric ceramics. When compared which other piezoelectric substances, both BaTiO3 and PbTiO3PbZrO3 have the following advantages: Advantages qHigh electromechanical transformation efficiency. wHigh machinability. eA broad range of characteristics can be achieved with different material compositions (high degree of freedom in characteristics design). rHigh stability. tSuitable for mass production, and economical. Murata, as a forerunner in the piezoelectric ceramic industry, offers an extensive range of products with piezoelectric applications.
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2. Properties of Piezoelectric Ceramics
Piezoelectric ceramics are a type of multi-crystal dielectric with a high dielectric constant and are formed by two processes : first, high temperature firing. After firing, they have the characteristic crystal structure shown in Fig. 1 (a) but do not yet exhibit the piezoelectric property because the electrical dipoles within the crystals are oriented at random and the overall moment of the dipoles is canceled out. To make ceramics piezoelectric they must be polarized. A DC electric field of several kV/mm is applied to the piece of ceramic to align the internal electrical dipoles in a single orientation (see Fig. 1 (b)). Due to the strong dielectric property of the ceramic, the dipole moment remains unchanged after the electric field is removed, and the ceramic thus exhibits a strong piezoelectric property (see Fig. 1 (c)). When an AC signal is applied to a piezoelectric ceramic (piezoelectric transducer) in a frequency matching the specific elastic frequency of the ceramics (which depends on the shape of the material), the ceramic exhibits resonance. Since the ceramic has a very high electromechanical transforming efficiency at the point of resonance, many applications use this resonance point. Also piezoelectric ceramics when molded in certain shapes have more than one point of resonance depending on vibration mode. In such a case, the vibration mode most suited for the application is selected.
(a) Electrodes
(b)
(c)
After firing
Polarization processing in strong DC field (Several kV/mm)
Overall, the polarization axes are oriented upward.
Residual Polarization The direction of polarization remains the same after the electric field is cut off.
Fig. 1 Polarization Processing of Piezoelectric Ceramics
3. Application of Piezoelectric Ceramics
Product applications for piezoelectric ceramics include the following categories : Murata has and is continuing to direct extensive research development efforts to the entire range of applications of piezoelectric ceramics listed in the right side. It is expected that the applications of piezoelectric ceramics will continue to extend into a broader range of industries as new piezoelectric materials are created. This application manual concentrates on applications with mechanical power sources and sensors which are now finding broader applications. Piezoelectric Applications qMechanical power sources (electrical-to-mechanical transducers) : Piezoelectric actuators, piezoelectric fans, ultrasonic cleaners, etc. wSensors (mechanical-to-electrical transducers) : Ultrasonic sensors, knocking sensors, shock sensors, acceleration sensors, etc. eElectronic circuit components (transducers) : Ceramic filters, ceramic resonators, surface acoustic wave filters, microforks, etc.
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!Note Please read rating and !CAUTION (for storage and operating, rating, soldering and mounting, handling) in this PDF catalog to prevent smoking and/or burning, etc.
This catalog has only typical specifications. Therefore, you are requested to approve our product specification or to transact the approval sheet for product specificaion before ordering.
P19E7.pdf 02.6.26
2 Characteristics of Piezoelectric Ceramics (PIEZOTITEr)
For using piezoelectric ceramics, it is important to first have an adequate knowledge of the properties of different piezoelectric materials before choosing a suitable type for a specific application. The following sections describe the major characteristic which need to be evaluated to determine the properties of piezoelectric ceramic materials.
1. Resonant Frequency and Vibration Mode
If an AC voltage of varying frequency is applied to a piezoelectric ceramic (piezoelectric transducer) of a certain shape, it can be seen that there is a specific frequency at which the ceramic produces a very strong vibration. This frequency is called the resonant frequency, fr, and depends on the ceramic's specific elastic vibration (resonance) frequency, which is a function of the shape of the material. Piezoelectric ceramics have various vibration modes (resonant modes) which depend on their shape, orientation of polarization, and the direction of the electric field. Each of these vibration modes have unique
Vibration Mode Shape/Vibration Mode
resonant frequencies and piezoelectric characteristics. Fig. 2 shows typical vibration modes in relation to the shapes of ceramic materials, the resonant frequency in each vibration mode, and the material constant symbols. In Fig. 2, the piezoelectric material constant symbols have the following meanings: N :Frequency Constant (described in Section 1). d :Piezoelectric Distortion Constant (described in Section 2). g :Voltage Output Constant (described in Section 2). k :Electromechanical Coupling Coefficient (described in Section 3). YE :Young's Modulus (described in Section 5). T :Dielectric Constant (described in Section 8).
Resonant Frequency (fr) Material Constant Symbol k d g YE
2
T
N
EP d
t d >15t
Radial Mode
P : Direction of polarization E : Direction of electric field
Np d
kp
d31
g31
Y11E
33T
Np
Thin disk with radial vibration mode. Polarization is oriented along the thickness of the disk.
R
a
t
Length Mode
EP R> 4a a > 3t
N31 R
k31
d31
g31
Y11E
33T
N31
Thin rectangular plate, with the direction of vibration orthogonal to the polarization axis and with a single point of resonance.
a
b
d
Longitudinal Mode
EP
R
R
N33 R
k33
d33
g33
Y33E
33T
N33
R> 2.5a,2.5b,2.5d
Square and cylindrical columns. Vibration is oriented along the direction of polarization. Only a single point of resonance.
R
t d
a
t
Thickness Mode
EP
10t V a,R,d
Nt t
kt
d33
g33
Y33E
33T
Nt
Disk and rectangular plates which are thin compared to their surface areas. They have multiple points of resonance in longitudinal vibration mode.
R
a
Shear Mode
t E P R> a > t
N15 t
k15
d15
g15
Y44E
11T
N15
Disk or rectangular plates, with the electric field orthogonal to the direction of polarization, causing a shear vibration along the surface.
Fig. 2 Typical Vibration Modes, Resonant Frequencies, and Material Constant Symbols of Piezoelectric Ceramics
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