Doping effect on crystal structure of BaTiO3 and magnetoelectric coupling of layered composites Tb1−xDyxFe2−y–BaTi0.99M0.01O3+δ

1.0 mol% Cr-, Mn- and Co-doped BaTiO3 composites have been synthesized as a kind of “green” piezoelectrics. The lattice constants of the doped BaTiO3 are calculated from their patterns of X-ray diffraction. The tetragonality (c/a) of these doped samples has been found to decrease in turn according to the order Cr-, Mn- and Co-doped BaTiO3, and be lower than that of pure BaTiO3. The transition temperature of ferroelectric to paraelectric phase and the accompanying latent heat of the transition have also been found to decrease in turn according to the order above for the doped BaTiO3. Bonded bilayer composites Tb1−xDyxFe2−y (TDF)–BaTi0.99M0.01O3+δ (M = Cr, Mn and Co) have been fabricated. Their ME effect has been investigated. The maximum value of the transverse ME voltage coefficients for the bilayers were observed to decrease in turn, from 586 to 445 mV cm−1 Oe−1, in the sequence of TDF–BaTi0.99Cr0.01O3+δ, TDF–BaTi0.99Mn0.01O3+δ and TDF–BaTi0.99Co0.01O3+δ. It indicates that tetragonality of the structure is a key factor in determining both the physical property of the doped BaTiO3 and the ME effect of the composite containing the doped BaTiO3.