New Piezoelectric Materials

Recently, many new piezoelectric materials have appeared as a consequence of the ability to observe and tailor crystal, polycrystaUine, and polymer stmctures on the nanoscale. Indeed the evolution of high-performance piezoelectric materials like PMN-PT, polypyrrole, IPMC, and other electroactive polymers promises to usher in a new generation of materials that offer advantages over PZT for dispensing apphcations. Meanwhile, compatibility problems in the fabrication of silicon, PZT, and other standard micromachining materials are being solved, offering the ability to apply PZT in ways not currently possible. 

Recently, electrets made with cellular stmctured polymers have received attention as new piezoelectric materials with a high piezoelectric 33 coefficient exceeding 100 pC/N. In particular, research on cellular polypropylene (PP) film has been conducted to improve both its physical characteristics and its applications (Neugschwandtner et al. 2000 Hillenbrand and Sessler 2000 Paajanen et al. 1998, 2001 Zhang et al. 2007). 

Discoveries of new piezoelectric materials started a new boom of research in the 1940s when A.V. Shubnikov predicted that piezoelectric properties would be found in amorphous and polycrystalline materials. His predictions were confirmed soon by observing that ferroelectric ceramics are strongly piezoelectric. The existence of piezoelectricity for certain synthetic and biological polymers has also been known for a long time. In particular, piezoelectricity in bone and tendon has been extensively studied. ... 

R. Y. Ting, "Evaluation of New Piezoelectric Composite Materials for Hydrophone AppUcations," presented at the Bernard Jaffe Memorial Colloquium, American Ceramics Society, 86 Meeting, Pittsburgh, 1984. 

In the ceramics field many of the new advanced ceramic oxides have a specially prepared mixture of cations which determines the crystal structure, through the relative sizes of the cations and oxygen ions, and the physical properties through the choice of cations and tlreh oxidation states. These include, for example, solid electrolytes and electrodes for sensors and fuel cells, fenites and garnets for magnetic systems, zirconates and titanates for piezoelectric materials, as well as ceramic superconductors and a number of other substances... 

Piezoelectric ceramics, which depend on lead compounds, are used to produce transducers and sensors which make possible ultrasound technologies used in wide-ranging medical and commercial applications, guidance and sensing systems used in defense and commerce, and in addition, new "smart materials" research projects. 

We have had smart materials as materials for a long time though the term is relatively new. Some of the first smart materials were piezoelectric materials, such as poly(vinylene fluoride), which emit an electric current when pressure is applied and change volume when a current is passed through it. Most smart materials are polymeric or have a critical portion of the smart system that is polymeric. 

In comparison to ordinary dielectrics, the permittivities of the so-called ferroelectric materials are about 103 times larger. The ferroelectric material can be transformed into a new type of material called piezoelectric material by heating the ferroelectric above its Curie temperature and then cooling it in a powerful electric field. A piezoelectric crystal changes its polarization once subjected to a mechanical strain. As a result, it can deform mechanically under an electric field or produce electric impulses as a result of mechanical impulses. Currently, piezoelectric materials are widely used as force or pressure transducers with fast response times and very sensitive output. Permittivities of common dielectric and ferroelectric materials are given in Table 1.9. 

With this background, we have proposed and developed a new purely electrical method for imaging the state of the polarizations in ferroelectric and piezoelectric material and their crystal anisotropy. It involves the measurement of point-to-point variations of the nonlinear dielectric constant of a specimen and is termed scanning nonlinear dielectric microscopy (sndm) [1-7]. This is the first successful purely electrical method for observing the ferroelectric polarization distribution without the influence of the screening effect from free charges. To date, the resolution of this microscope has been improved down to the subnanometer order. 

Looking beyond ceramic materials to elec-trets, polymer and elastomeric piezoelectric materials, and so-caUed electroactive materials, a wide-open field of research in high-strain piezoelectric materials is appearing. Using the same technology to manipulate the chemical and physical stractures of complex ionic or nanotube-imbibed polymers, strains of well over 50 % have been obtained in this new class of material, many examples of which are biocompatible. Improvements in reliability, tolerance of extreme ambient conditions, and modeling are important areas that remain to be considered. 

Arnau A (ed) (2004) Piezoelectric transducers and applications. Springer, Berlin, Heidelberg Bush-Vishniac IJ (1999) Electromechanical Sensors and Actuators. Springer, New York, NY Galassi C et al (2000) Piezoelectric materials Advances in science, technology and applications. 

Krempl P, Schleinzer G, Wallnofer W (1997) Gallium phosphate, GaP04 A new piezoelectric crystal material for high-temperature sensorics. Sens Actuators A61 361-363... 

Rosen CZ, Hiremath BV, Newnham R (eds) (1992) Piezoelectricity. Springer-Verlag, New York Roy S, Basu S (2002) Improved zinc oxide film for gas sensor apphcations. BuU Mater Sci 25 513-515 Sanchez-Pedreno JAO, Drew PKP, Alder JF (1986) The investigation of coating materials for the detection of nitrobenzene with coated quartz piezoelectric crystals. Anal Chim Acta 182 285-291 Scheide EP, Taylor JK (1974) Piezoelectric sensor for mercury in air. Environ Sci Technol 8 1087-1091 Schulz M, Sauerwald J, Richter D, Fritze H (2009) Electromechanical properties and defect chemistry of Mgh-temper-ature piezoelectric materials. Ionics 15 157-161... 

Uchino, K. (1995) New piezoelectric devices for smart actuator/sensor systems, in Smart Materials Symposium (ed. S. Sirisoonthom), National Metal and Materials Technology Center (MTEC), Bangkok, Thailand, pp. 1-110. 

Kenji Uchino (2010) Advanced piezoelectric materials. Woodhead Publishing Limited, Oxfind/Cambridge/ Philadelphia/New Delhi. Uchino. Advanced piezoelectric... 

Schwartz, M. M ed. 2002a. Encyclopedia of Materials, Parts, and Finishes, 2nd ed. Boca Raton, FL CRC Press available online. This second edition of the encyclopedia covers the new materials that have been invented or modified in recent years (including matrix composites, nanostructures, smart piezoelectric materials, shape memory alloys, and inter-metallics), and updates information on basic materials as well. Many tables and figures, but no references. 

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