Ferroelectric/piezoelectric

Ferroelectric—polymer composite devices have been developed for large-area transducers, active noise control, and medical imaging appHcations. North American Philips, Hewlett-Packard, and Toshiba make composite medical imaging probes for in-house use. Krautkramer Branson Co. produces the same purpose composite transducer for the open market. NTK Technical Ceramics and Mitsubishi Petrochemical market ferroelectric—polymer composite materials (108) for various device appHcations, such as a towed array hydrophone and robotic use. Whereas the composite market is growing with the invention of new devices, total unit volume and doUar amounts are small compared to the ferroelectric capacitor and ferroelectric—piezoelectric ceramic markets (see Medical imaging technology). 

In the broad range of ceramic materials that are used for electrical and electronic apphcations, each category of material exhibits unique property characteristics which directiy reflect composition, processing, and microstmcture. Detailed treatment is given primarily to those property characteristics relating to insulation behavior and electrical conduction processes. Further details concerning the more specialized electrical behavior in ceramic materials, eg, polarization, dielectric, ferroelectric, piezoelectric, electrooptic, and magnetic phenomena, are covered in References 1—9. 

The main categories of electrical/optical ceramics are as follows phosphors for TV, radar and oscilloscope screens voltage-dependent and thermally sensitive resistors dielectrics, including ferroelectrics piezoelectric materials, again including ferroelectrics pyroelectric ceramics electro-optic ceramics and magnetic ceramics. 

PVDF is mainly obtained by radical polymerisation of 1,1-difluoroethylene head to tail is the preferred mode of linking between the monomer units, but according to the polymerisation conditions, head to head or tail to tail links may appear. The inversion percentage, which depends upon the polymerisation temperature (3.5% at 20°C, around 6% at 140°C), can be quantified by F or C NMR spectroscopy [30] or FTIR spectroscopy [31], and affects the crystallinity of the polymer and its physical properties. The latter have been extensively summarised by Lovinger [30]. Upon recrystallisation from the melted state, PVDF features a spherulitic structure with a crystalline phase representing 50% of the whole material [32]. Four different crystalline phases (a, jS, y, S) may be identified, but the a phase is the most common as it is the most stable from a thermodynamic point of view. Its helical structure is composed of two antiparallel chains. The other phases may be obtained, as shown by the conversion diagram (Fig. 7), by applying a mechanical or thermal stress or an electrical polarisation. The / phase owns ferroelectric, piezoelectric and pyroelectric properties. 

A wide array of ferroelectric, piezoelectric and pyroelectric materials have titanium, zirconium and zinc metal cations as part of their elemental composition Many electrical materials based on titanium oxide (titanates) and zirconium oxide (zirconates) are known to have structures based on perovskite-type oxide lattices Barium titanate, BaTiOs and a diverse compositional range of PZT materials (lead zirconate titanates, Pb Zr Tij-yOs) and PLZT materials (lead lanthanum zirconate titanates, PbxLai-xZryTii-yOs) are among these perovskite-type electrical materials. 

Combustion synthesis has been used to produce complex oxide materials, such as ferrites and ferroelectric, piezoelectric, and superconducting materials. In these systems, the heat required for SHS is supplied by the heat released from the reac-... 

Table 27.5 lists applications of some of the most commercially important mixed metal, perovskite-t5q)e oxides, and illustrates that it is the dielectric, ferroelectric, piezoelectric (see Section 13.9) and pyroelectric properties of these materials that are exploited in the electronics industry. 

The solids discussed in the remainder of this chapter have one thing in common They exhibit various polar effects, such as piezoelectricity, pyroelectricity, and ferroelectricity. Piezoelectric crystals are those that become electrically polarized or undergo a change in polarization when subjected to a stress, as shown in Fig. 15.12c to /. The application of a compressive stress results in the flow of charge in one direction in the measuring circuit and in the opposite direction for tensile stresses. Conversely, the application of an electric field will stretch or compress the crystal depending on the orientation of the applied field to the polarization in the crystal. 

Until the late sixties the only known ferroelectrics, piezoelectrics, and pyroelectrics were certain inorganic monocrystals, or polycrystalline ceramics like lead titanate zirconate perovskites. Other known materials with macroscopic polarization were electrets, (for example mixmres of beeswax and rosin) in which the polarization was produced by application of the electric field in the melted state and then by cooling and the solidification of the polarized material. 

One of the formative works demonstrating the feasibility of 9/49- SSNMR was the 1993 work by Dec et al. [48], who examined a series of ferroelectric, piezoelectric, and related materials using Zr,... 

Perovskite compounds have the general formula ABX3 for the purposes of this study, we are concerned with ATiOa derivatives. Perovskites may be ferroelectric, piezoelectric, etc., and due to their low cost, are currently being re-explored for a variety of purposes, such as in solar cells [124] and catalysts [125,126]. In many cases, the structure—property relationships in the ATi03 compound are unclear. The use of SSNMR for... 

The requirement for inorganic electronic materials prepared at low temperatures has stimulated enormous activity in the heterometal oxide field. The sol-gel technique using metal alkoxides has been especially effective in producing ferroelectric, piezoelectric, and pyroelectric materials, e.g. BaTiOz " LiNbOz " LiTaOs " PbTiOs Pb(Zr,Ti)03(PZT) (Pb,La) (Zr,Ti)03(PLZT) 2 Pb(Fe,Nb)03 andPb(Mg,Nb)03. ... 

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