Zirconate FERROELECTRICS

The development of active ceramic-polymer composites was undertaken for underwater hydrophones having hydrostatic piezoelectric coefficients larger than those of the commonly used lead zirconate titanate (PZT) ceramics (60—70). It has been demonstrated that certain composite hydrophone materials are two to three orders of magnitude more sensitive than PZT ceramics while satisfying such other requirements as pressure dependency of sensitivity. The idea of composite ferroelectrics has been extended to other appHcations such as ultrasonic transducers for acoustic imaging, thermistors having both negative and positive temperature coefficients of resistance, and active sound absorbers. 

Some perovskites are widely used as piezo-transducers, BaTi03 for example, and lead zirconate (PbZr03) which is a well-known ferroelectric material sensitive to stresses. Also, some perovskites are good pyro-transducers that is, heat causes electric polarization of them. 

Merklein, S. Sporn, D. Schonecker, A. 1992. Crystallization behavior and electrical properties of wet-chemically deposited lead zirconate titanate. In Ferroelectric Thin Films III, edited by Tuttle, B. A. Myers, E. R. Desu, S. B. Larsen, P. K. Mat. Res. Soc. Symp. Proc. 310 263-268. 

Losego, M. D. Trolier-McKinstry, S. 2004. Mist deposition of micron thick lead zirconate titanate thick films. In Ferroelectric Thin Films XII, edited by Hoffmann-Eifert, S. Funakubo, H. Kingon, A. I. Koutsaroff, I. Joshi, V. Mat. Res. Soc. Symp. Proc. 784(C11.28) l-6. 

In lead zirconate, PbZr03, the larger lead ions are displaced alternately from the cube comer sites to produce an antiferroelectric. This can readily be converted to a ferroelectric by the substitution of Ti4+ ions for some of the Zr4+ ions, the maximum value of permittivity occurring at about the 50 50 mixture of PbZrC>3 and PbTiC>3. The resulting PZT ceramics are used in a number of capacitance and electro-optic applications. The major problem in the preparation of these solid solutions is the volatility of PbO. This is overcome by... 

Lead titanate (PT), 5 583 as ferroelectric, 5 605-608 Lead titanate, 14 797 25 47 Lead titanate-zirconates, 14 797 Lead transport mechanisms, 25 394 Lead trioxide, 14 787-788 Lead users, role in product design, 5 761, 766... 

Approximately ten years ago, it was first reported by Haertling and Land (jj that optical transparency was achieved in a ferroelectric ceramic material. This material was, in reality, not just one composition but consisted of a series of compositions in the lanthanum modified lead zirconate-lead titanate (PLZT) solid solution region. The multiplicity of compositions, each with different mechanical, electrical and electrooptic properties has led to a decade of study in defining the chemical and structural nature of these materials in understanding the phenomena underlying their optical and electrooptic properties and in evaluating the practicality of the large number of possible applications (2-12),... 

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. 

Certain glass-ceramic materials also exhibit potentially useful electro-optic effects. These include glasses with microcrystallites of Cd-sulfoselenides, which show a strong nonlinear response to an electric field (9), as well as glass-ceramics based on ferroelectric perovskite crystals such as niobates, titanates, or zirconates (10—12). Such crystals permit electric control of scattering and other optical properties. 

Longtu, Li. et al. (1990) Lead zirconate titanate ceramics and monolithic piezoelectric transformer of low firing temperature, Ferroelectrics, 101, 193-200. 

There are certain crystals in which dipoles are spontaneously aligned in a particular direction, even in the absence of electric field. Such substances are called ferroelectric substances and the phenomenon is called ferroelectricty. The direction of polarisation in these substances can be changed by applying electric field. Baruion titanate (BaTi03), sodium potassium tartarate (Rochelle salt), and potassium hydrozen phosphate (KH2I04) are ferroelectric solids. If the alternate dipoles are in opposite directions, then the net dipole moment will be zero and the crystal is called anti-ferroelectric. Lead zirconate (PbZr03) is an anti-ferroelectric solid. 

A simple quantitative model, with no adjustable parameters, is developed for the finite size effect of ferroelectric particles on the Curie transition temperature. As the size of ferroelectric particles decreases, the Curie temperature decreases. Based on our model for lattice contraction and the Landau-Ginsburg-Devonshire (LGD) phenomenological theory, size effects on Curie temperature of lead zirconate titanate PbZri. Ti Oj (PZT, x > 0.6) are considered. It is shown that Curie temperature of PZT (x > 0,6) decreases with decreasing particle size. The predictions of our equation are in agreement with the experimental results. 

Haun M. J., Furman E., Jang S. J. and Cross L. E., Thermodynamic theory of the lead zirconate-titanate solid solution system, Ferroelectrics 99 (1989) 13 Parts I to V. 

A broad range of electronic ceramic materials have been prepared by CSD, but three material systems have dominated the field of ferroelectric thin films. These include the perovskites PbZr03-PbTi03 (lead zirconate titanate PZT), BaTi03-SrTi03 (barimn strontium titanate BST), and the layered perovskite SrBi2Ta209 (strontium bismuth tantalate SBT). The extensive solid solubility ranges... 

As concerns the piezoelectric layer, the first choice often goes to lead zirconate titanate (PZT) because of its outstanding piezoelectric, pyroelectric and ferroelectric properties. Nickel ferrite (NF) is not widely employed for the synthesis of the multilayered composites owing to a strong reduction of its magnetization in the lower grain size limit. However, a very thin NF layer can help to attain entirely different properties and, hence, this material has been chosen as a sandwiched layer in the present work. 

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