Linear electromechanical properties

Linear electromechanical properties - elastic, piezoelectric and dielectric -including their temperature coefficients for a-quartz are summarized in Table 7.2. Temperature dependence of the piezoelectric coefficients d, du is moreover displayed in Fig. 7.4. This temperature behavior is very important for the applications of quartz in sensors. 

Activation and conductivity at room temperature are problems that can be addressed by the incorporation of other electronic structures that increase carrier transport. Crystal morphology is an important parameter in the boron doping process to determine uncompensated acceptors (Aa-Ad) for different crystal facets as a function of doping concentration. The temperature coefficient of resistance for a CVD diamond film can be changed by boron doping. As conductivity depends on the crystal phase, the combined electromechanical properties can be exploited in sensor applications both for resistive temperature detectors and for pressure transdu-cers. " As electrical conductivity is related linearly with boron concentration, a better-controlled process may allow for the development of better semiconductor devices improving crystal quality and operating limits. ... 

Bogs, M., Beige, H., Pitzius, R, Schmitt, H. Linear and nonlinear dielectric, elastic and electromechanical properties of Pb(Sci/2Tai/2)03 ceramics. Ferroelectrics 126,197-202 (1992)... 

Book content is otganized in seven chapters and one Appendix. Chapter 1 is devoted to the fnndamental principles of piezoelectricity and its application including related histoiy of phenomenon discoveiy. A brief description of crystallography and tensor analysis needed for the piezoelectricity forms the content of Chap. 2. Covariant and contravariant formulation of tensor analysis is omitted in the new edition with respect to the old one. Chapter 3 is focused on the definition and basic properties of linear elastic properties of solids. Necessary thermodynamic description of piezoelectricity, definition of coupled field material coefficients and linear constitutive equations are discussed in Chap. 4. Piezoelectricity and its properties, tensor coefficients and their difierent possibilities, ferroelectricity, ferroics and physical models of it are given in Chap. 5. Chapter 6. is substantially enlarged in this new edition and it is focused especially on non-linear phenomena in electroelasticity. Chapter 7. has been also enlarged due to mary new materials and their properties which appeared since the last book edition in 1980. This chapter includes lot of helpful tables with the material data for the most today s applied materials. Finally, Appendix contains material tensor tables for the electromechanical coefficients listed in matrix form for reader s easy use and convenience. 

Piezoelectricity. The Piezoelectric Ejfect. Because all acoustic gravimetric sensors are based on the phenomenon of piezoelectricity, it seems appropriate to discuss briefly the effect itself. Piezoelectricity was first observed by the Curie brothers (Jaques and Pierre) in 1880 [258]. It is a reversible phenomenon, consisting of linear electromechanical interactions between mechanical and electrical properties in certain crystals (Fig. 52). The effect is generated, as already men-... 

Polarization which can be induced in nonconducting materials by means of an externally appHed electric field is one of the most important parameters in the theory of insulators, which are called dielectrics when their polarizabiUty is under consideration (1). Experimental investigations have shown that these materials can be divided into linear and nonlinear dielectrics in accordance with their behavior in a realizable range of the electric field. The electric polarization PI of linear dielectrics depends linearly on the electric field E, whereas that of nonlinear dielectrics is a nonlinear function of the electric field (2). The polarization values which can be measured in linear (normal) dielectrics upon appHcation of experimentally attainable electric fields are usually small. However, a certain group of nonlinear dielectrics exhibit polarization values which are several orders of magnitude larger than those observed in normal dielectrics (3). Consequentiy, a number of useful physical properties related to the polarization of the materials, such as elastic, thermal, optical, electromechanical, etc, are observed in these groups of nonlinear dielectrics (4). 

Electromechanical coupling coefficient is higher for LGS than for quartz. Some of the LGS non-linear material coefficients are pubhshed in Sorokin et al. (1996). Temperature coefficients published by different authors show values widely scattered. For material properties and their temperature coefficierrts see Tables 7.7 and 7.8. (Adachi et al. 1999 Bohm et al. 1999, 2000 Ilyaev et al. 1986 Kaminskii et al. 1983a,b, 1984 Onozato et al. 2000 Pisarevskii et al. 1998 Silvestrova et al. 1986, 1987, 1993 Sorokin etal. 1996). 

The electrostrictive behavior of P(VDF-CTFE) copolymers was investigated (Li et al. 2004 Li et al. 2006). A high electromechanical response was obtained in these copolymer films. As other PVDF-based polymers, the processing condition plays a very critical role on its properties. For a well-stretched and annealed P (VDF-CTFE) 88/12 copolymer film, a longitudinal electrostrictive strain as much as 5.5 % was obtained. A linear relationship between the strain response and the was observed, which indicates the electrostrictive nature of the electromechanical response in P(VDF-CTFE) copolymers. The corresponding electric field-related electrostrictive coefficient for the copolymer film is obtained as Mss = —1.23 0.02 X 10 (m /V ) (Li et al. 2006). 

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