Fe Doping Of Batio <sub> 3 </ Sub> (fe-of Batio <sub> 3 </ Sub>)-tb <sub> 1-x </ Sub> Dy <sub> The X </ Sub> Of Fe <the Sub > 2-y </ Sub> Composite Structure Of Magnetic Effect

In this paper we discussed the giant recoverable electrostrain effect in aged Fe-doped BaTiO₃,and the magnetoelectric (ME) effect in bilayers and tribilayers of Fe- BaTiO₃-Tb_1-xDy_xFe_2-y Electric-field-induced 90°domain switch-ing is known to be able to generate huge strain, as it involves the exchange of nonequal crystalline axis.However, such a huge electrostrain effect is normally irrecoverable (i.e., can-not reappear under field cycles), thus renders the effect useless. This is because domain switching is intrinsically an irreversible effect due to the energetic equivalence of different domain states. However, our mechanism utilizes a universal "symmetry-conforming principle" of point defects(defect symmetry principle) to generate a restoring force for domain switching and consequently realize a reversible domain switching.The symmetry-conforming property of point defects provides an intrinsic restoring force for reversible domain switching.Based on this defect-mediated reversible domain-switching mechanism, a giant recoverable electrostrain of 0.75% has been achieved in aged Fe-doped BaTiO₃ single crystals and a large electrostrain of 0.15% was achieved in aged Fe-doped BaTiO₃ ceramics.Fe-doped BaTiO₃ has been synthesized with sol-gel technique . The perovskite of Fe-doped BaTiO₃ was found in tetragonal structure as pure BaTiO₃. Its transformation point of ferroelectric to paraelectric and the latent heat of the transformation were observed at 103.27℃and 169.9 J/mol, respectively. They are a little less than those for pure BaTiO₃,110.66℃and 227.6 J/mol respectively.Layered composites Tb_1-xDy_xFe_2-y/ Fe-BaTiO₃ have been fabricated. Their magnetoelectric (ME) effect has been investigated. The transverse ME voltage coefficient for the bilayer Tb_1-xDy_xFe_2-y-BaTio.99Feo.01O3 and the trilayer Tb_1-xDy_xFe_2-y-BaTi_0.99Fe_0.01O₃-Tb_1-xDy_xFe_2-y can reach 578 (mV Oe^-1 cm^-1) and 2100 (mV Oe^-1 cm^-1), respectively, under a bias magnetic field 350 Oe at room temperature. Those are about 50% larger than those for the bilayer and trilayer composed by pure BaTiO₃. It suggests that the doped BaTiO₃ can be a new choice of piezoelectrics to compose ME composites.