Preparation of Ferroelectric Ceramics

The Synthesis and Fabrication of Ceramics for Special Application 315 17.3.11. Preparation of Ferroelectric Ceramics 17.3.11.1. Introduction... 

As already mentioned by Sakka in the Preface of the Handbook of Sol-Gel Science and Technology published in 2005 [12], the first apphcation of the sol-gel oxide powders for obtaining dense ceramics was published by Brown and Mazdiyasni already in the early 1970 and was referred to as the preparation of ferroelectric ceramics [21],... 

In previous papers (9,31-33) we have investigated the dielectric and electret properties of the composite pdy(methyl methacrylate) (PMMAVBaTiO, ceramic system. The 0-3 type composites used in the studies were prepared by polymerization of methyl methacrylate (MMA) in which fine particles of ferroelectric ceramics BaHO, were dispersed. The BaTiOt ceramics were ofarained by the known method of triple sintering of BaCO) and TK), in stoichioaietiic ratio. The final process was conducted at about 1620 K for 3 h. resulting in a ceramic density of 5.57 X 10 kg/m This was pulverized and sifted... 

Ceramics. The properties of ferroelectrics, basically deterrnined by composition, are also affected by the microstmcture of the densifted body which depends on the fabrication method and condition. The ferroelectric ceramic process is comprised of the following steps (10,24,25) (/) selection of raw oxide materials, (2) preparation of a powder composition, (J) shaping, (4) densification, and (5) finishing. 

These compounds can be referred to as the ferroelectric family A5B3X19. PbsW C Fio, a basic compound of the family, was discovered and investigated by Ravez, Abrahams, Marsh, Arquis and Chaminade [428]. A significant number of compounds that belong to the ferroelectric family A5B3X19, where A = Sr, Ba, Pb and B = Al, Ti, V, Cr, Fe, Ga, Mo, W [428 - 437] have been prepared and investigated in the form of powder, ceramics or small single crystals. 

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... 

In this work, sol-gel method was used to prepare BaTiOj powder, then ceramic electrode was made using this powder after removing binder, sintering and firing silver. Finally, the ceramics are used for the study of ferroelectric and dielectric properties. 

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... 

Shrout, T. R., and Halliyal, A., Preparation of lead-based ferroelectric relaxors for capacitors, Am. Ceram. Bull., 66, 704 (1987). 

Ceramic PLZT has a number of structures, depending upon composition, and can show both the Pockels (linear) electro-optic effect in the ferroelectric rhombohedral and tetragonal phases and the Kerr (quadratic) effect in the cubic paraelectric state. Because of the ceramic nature of the material, the non-cubic phases show no birefringence in the as-prepared state and must be poled to become useful electro-optically (Section 6.4.1). PMN-PT and PZN-PT are relaxor ferroelectrics. These have an isotropic structure in the absence of an electric field, but this is easily altered in an applied electric field to give a birefringent electro-optic material. All of these phases, with optimised compositions, have much higher electro-optic coefficients than LiNb03 and are actively studied for device application. 

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