Ferromagnetic materials various properties

Sintered ceramics made of lead-zirconium titanate (PZT Pb(Tii jZr,)03 x S 0.5) are usually used for phoioacoustic experiments [105, 106]. The unit cell of the lead-zirconium titanate has a perovskite structure. Below the Curie temperature (328 °C for the PZT-4 (Vemitron) used by us [24]), the cells are tetragonally deformed, i.e., positive and negative charges are shifted and electric dipole moments are produced. In analogy to ferromagnetism, domains with randomly distributed polarization direction are formed. By the application of an electric field, these can be orientated in a preferred direction, and the sintered polycrystalline ceramic is then remanently polarized. The properties of these anisotropic piezoelectric materials are described by various parameters which depend on the polarization and deformation direction. In the common terminology, the < ordinate system shown in Fig. 3 is obtained for the cylindrical piezoelectric crystals [24]. 

To isolate the metal particles, the matrix material is easily removed by washing with various solvents. The solid mixture is treated with benzene or toluene and yields metal suspensions which when dried and exposed to air heat up and smoke and sometimes ignite the powders then consist of mainly metal oxides with loss of ferromagnetic properties. Washing the powders with octanol renders them air stable by forming a protective film over the particles. Excess octanol can be removed by washing the metal powders with methanol, ethanol, or isopropanol. Such washed powders exhibit air sensitivity. 

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