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Journal of Tongren University 20 1 1
General situation and development trend of high temperature piezoelectric materials
Wei Shi, Ran Yaozong, Zuo Jianghong, Wang Qiang, Tao Tao, Ou Yongkang
(Department of Physics and Electronic Science, Tongren College, Guizhou 554300)
Abstract: The research status of high temperature piezoelectric materials is introduced. The structure and research status of perovskite, tungsten bronze, bismuth layered and alkali niobate piezoelectric ceramics are reviewed. The research direction and development trend of high Curie point piezoelectric ceramics are pointed out.
Key words: piezoelectric ceramics; Curie temperature; ferroelectric ceramics
China Library ClassificationNo.: TQ 174 Document IdentificationNo.: A DocumentNo.:1673-9639 (2011) 05-0140-03.
1. Introduction
Piezoelectric ceramics are widely used in aviation, energy, automobile manufacturing, communication, home appliances, detection and computers, and are an important part of electronic components such as filters, transducers, sensors and piezoelectric transformers. [1][2]3[3] Due to the depolarization of piezoelectric materials in an environment higher than the Curie temperature (T c) of the materials, the piezoelectric properties will decay or even disappear. Therefore, in order to ensure the normal use of devices, the application environment of piezoelectric devices is generally below half the Curie temperature (T c) of piezoelectric materials. [4]
The service temperature of civil electronic products is usually below 75℃, and the service temperature of some military electronic products is around 125℃. However, with the rapid development of science and technology, especially the development of geological exploration, aerospace and automobile technology, piezoelectric devices are required to constantly challenge the limits of high-temperature working environment, and the key to solve this problem is to prepare materials with higher Curie temperature. The main high-temperature working environment exists in geological exploration, aerospace, nuclear industry and automobile industry. The temperature of these working environments is mostly above 200℃, even as high as 900℃. Petroleum exploitation and geological exploration have the widest demand for high-temperature materials, which is one of the main driving forces to promote the research of high-temperature piezoelectric ceramics. For example, during drilling, when the probe sensing system collects data such as temperature, pressure, flow rate, density and chemical composition, the temperature near the probe can reach 200℃, and it will increase with the increase of drilling depth.
Date of receipt: 20 1 15-03
It will rise. In the aerospace field, the requirements for high-temperature devices are more stringent. For example, the highest temperature on the surface of the moon can reach 330℃, and the surface of Venus can reach 460℃. The devices that leave the earth and enter space are required to work stably at high temperature for more than 65,438+10,000 hours. With the development of automobile industry, the degree of automation, informationization and intelligence is getting higher and higher, which benefits from the use of hundreds of sensing devices, including high-temperature sensing devices for monitoring engine speed and angle, braking and fuel system. [6][7][8] In addition, the nuclear industry and the flame monitoring system also have great demand for high-temperature devices.
2. Several classifications of high temperature piezoelectric materials.
At present, high T c piezoelectric materials mainly include perovskite structure system, tungsten bronze structure system, bismuth layered structure system and alkali metal niobate system. Table 1 compares the relevant important electrical performance data of typical materials in these four systems.
Fund Project: Supported by the Doctoral Start-up Fund of Tongren College 20 10 (No.:DS 100 1).
About the author: Wei Shi (1975-), male, Miao nationality, Ph.D., lecturer in the Department of Physics and Electronic Science of Tongren University.
The 5th Shiwei: Overview and Development Trend of High Temperature Piezoelectric Materials 14 1
2. 1. perovskite structure
Lead zirconate titanate PZT ceramics with perovskite structure have excellent electrical properties, such as piezoelectric, dielectric and photoelectric properties. They were first successfully trial-produced by Jaffe et al. [9] in 1954, and are widely used in the field of electronic information. 2.3. Bismuth layer.
Since the discovery of bismuth layered compounds by Aurivillius in 1949, its peculiar crystal structure and high T _ C have attracted extensive attention. Bismuth layered piezoelectric ceramics are widely studied for preparing electronic components such as sensors, transducers and memories. Therefore, PZT and PZT binary and ternary ceramic systems have become the most commercialized and mature piezoelectric materials. But the Curie temperature of PZT ceramics is not high (T c
Figure 1 perovskite structure schematic diagram
Its chemical general formula is ABO 3, and its perovskite structure can be described by a simple cube. The A-site ions are located in the eight corners of the hexahedron, the oxygen ions are located in the six face centers of the hexahedron, and the B-ion is located in the center of the hexahedron. The whole crystal is formed by repeating the arrangement of such units. PbTiO _ 3, another piezoelectric ceramic, has a perovskite structure with high Curie temperature (T c ~490℃), low dielectric constant, high voltage electroactivity and large piezoelectric anisotropy. The temperature coefficient of the third harmonic is the smallest among the existing ceramic materials, and the piezoelectric constant D _ 33 is only 60 ~ 70 PC/n, which limits its application range and is only used for high-temperature ultrasonic transducers. [ 15][ 16]
2.2. Tungsten bronze system
The chemical general formula of tungsten bronze system is A 6B 10O 30, and lead metaniobate (PbNb2O3) is the earliest discovered tungsten bronze ferroelectric.
[ 17]
Pbnb _ 2o _ 6 has high T _ c (570℃) and large anisotropy of piezoelectric effect (d 33/d 3 1 = 10, KT >; K p), a very low mechanical quality factor (Q m = 10 or so), can be used for high temperature ultrasonic transducers. The ferroelectric phase of lead metaniobate needs to be formed at high temperature (1230℃), but it is metastable at room temperature. In order to improve the sintering and piezoelectric properties of lead metaniobate, it needs to be doped and modified, such as using monovalent metal ion M+
Or divalent metal ion M 2+
Replace the lead. [ 18]
After the discovery of lead metaniobate piezoelectric ceramics, composite tungsten was discovered.
Bronze structural compounds, such as
Lead 4Na 2Nb 10O 30
and
Ba 4-2x Ag 2+x La x Nb 10O 30 also has a high glass transition temperature.
Cabi4ti4o15 [19] (TC = 790℃), Bi 3TiNbO 9[20](T c =940℃) and (NB0.5bi0.5) Bi4ti4o15 (TC = 600℃). Generally speaking, they have low dielectric constant, sintering temperature and aging rate, excellent insulation resistance and withstand voltage characteristics, very high T c and obvious anisotropy of electromechanical coupling coefficient, which makes them suitable for piezoelectric materials at high temperature and high frequency. However, due to the low symmetry of bismuth layered structure and its plate-like crystal characteristics, the E c of the system is very large and polarization is very difficult, which usually needs to be carried out at high temperature. On the other hand, because its spontaneous polarization is limited by two dimensions, its piezoelectric activity is very low, and d 33 is generally less than 20 PC/N. 2.4 Alkali metal niobate
Alkali metal niobate, with chemical formula of ANbO 3, is the most representative.
Lithium niobate (LiNbO 3)[2]3 is also the most widely used. Lithium niobate is a ferroelectric crystal with the highest T _ c (1210℃) and the largest spontaneous polarization (about 0.7C/m2 at room temperature). It is a twisted perovskite structure compound (LiNbO 3 crystal structure). However, the cost of lithium niobate crystal is high, and the preparation of lithium niobate ceramics is difficult. Because the piezoelectric activity of LiNbO _ 3 is low, and the d33 of LiNbO _ 3 single crystal is only 6pC/N, it can not meet the requirements of piezoelectric devices, which seriously limits its application in the piezoelectric field. Therefore, people have improved their piezoelectric activity by replacing lithium ions with other alkali metal ions, and studied a series of multi-element alkali metal niobate compounds. For example, 0.2Sr 2TaO 7-0.8Sr 2Nb 2O 7(SNST) single crystal, Curie temperature (T c ~ 1 125℃) is similar to LiNbO 3, and the junction is tested.
The results show that the crystal still has piezoelectric properties at 1000℃, and the piezoelectric constant is d 33 ~ 3 PC/n. [2 1] In the Patent of High Temperature Piezoelectric Materials published by Pennsylvania State University in 2007, YCaO(BO3) 3(YCOB) and GDCA4O.
discuss
From the previous review, it is found that the Curie temperature (T c) and piezoelectric constant (d 33), two key indexes of piezoelectric ceramics, approximately obey a simple inverse relationship, that is, the piezoelectric activity of high T c piezoelectric ceramics.
142 Journal of Tongren University 20 1 1 year
For example, when Curie temperature T c> is 500℃, its piezoelectric constant is d 33.
Fig. 2 Curie temperature of typical piezoelectric ceramics is related to.
Correlation of piezoelectric constants
4. Conclusion
Preparation of piezoelectric materials with high Curie temperature and good piezoelectric properties is the future development trend. By improving the preparation process and technology, integrating the advantages of perovskite structure with better piezoelectric activity and bismuth layered structure with higher Curie temperature, it is a problem to be solved to achieve a breakthrough in the preparation of new materials.
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Development of High Temperature Piezoelectric Ceramics
Wei, Ran Yaozong, Zuo Jianghong,,, Ou Yongkang
(Department of Physics and Electronic Science, Tongren University; China Guizhou Tongren 554300)
Abstract: Piezoelectric materials with high Curie temperature are reviewed, including tungstate, bismuth layered structure, perovskite piezoelectric ceramics and corundum structural ceramics. The research progress of four types of high Curie piezoelectric ceramics with different structures is reviewed. In addition, the research direction and development trend of piezoelectric ceramics are also discussed.
Key words: piezoelectric ceramics; High Curie temperature; Ferroelectric characteristics
(Editor Li Zongbao)
(Continued from page 124)
Science, 200 1, (7).
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Leisure, sports, leisure sports
Juan Wang
School of Physical Education, Jiangsu University of Science and Technology; Zhenjiang Jiangsu, 2 12003)
Abstract: With the rapid development of leisure and sports research, people began to pay attention to some basic theoretical issues, such as the relationship between leisure and sports and the concept of leisure sports. Starting from the concept of leisure, leisure has become a historical necessity. By analyzing the changes of sports values, the historical basis of leisure sports prosperity is obtained.
Keywords: leisure; Sports; leisure sport
(Editor Lu Nana)