Composite ferroics

Composite ferroics. Ingenious experiments have been performed with composites made from a ferroic and another material (Newnham Cross, 1981 Lynn et al, 1981 Rittenmeyer et al, 1982 Safari et al, 1982). For example, in a piezoelectric like PZT, the piezoelectric voltage coefficient g can be defined for a given direction (say Z = 33) thus, 33 = where d and k stand for piezoelectric coefficient... 

The materials with ME effect consist of about 50 % composites and 25 % single phase systems, which are the secondary ferroics. The other 25 % include solid solutions, laminar structures consisting of several layers with thickness about one millimeter as well as nanostructures in the form of thin films, nanorods etc. 

The information about nanocrystalline ferroic powders fabricated by various chemical synthesis technologies is reported in Table 5.2. Their possible applications are also listed. Powders of the same ferroics for two different applications might be obtained by different techniques since the requirements of size distribution, morphology, agglomeration and impurity composition are determined by different technological conditions. For example, barium titanate is a dielectric with high dielectric constant and it is widely used in multilayer ceramic capacitors, whereas semiconducting properties of rare-earth doped BaTiOs are important for thermistors. 

The fifth chapter presents detailed review of technological aspects of ferroic nanoparticles fabrication. We present the detailed information about methods of chemical synthesis of above nanoparticles. Among them are hydrothermal, sol-gel and coprecipitation methods. We also present the method of unstable compounds decomposition. The combined synthesis methods have also been discussed. Namely, we consider mechanochemical, sonochemical and template synthesis methods. The main idea of these methods is to control the dispersity and agglomeration degree of nanoparticles by inspection of nucleation and growth of a new phase. Self-assembly and self-organization of ferroic nanoparticles as well as composites formation on their base by means of colloidal processes have also been considered. 

Nan, C.W., U, M and Huang, J.H. (2001) Calculations of giant magnetoelectric effects in ferroic composites of rare-earth-iron alloys and ferroelectric polymers. Phys. Rev. B. 63, 144415. 

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