Raman scattering, electronic structure and microwave dielectric properties of Ba([Mg1−xZnx]1/3Ta2/3)O3 ceramics

Effects of Zn substitution for Mg on the crystal structure, lattice vibrations and microwave dielectric properties of Ba(Mg_1/3,Ta_2/3)O₃ (BMT) ceramics were investigated. Raman scattering spectra for Ba([Mg_1−xZn_x]_1/3Ta_2/3)O₃ (BMZT) ceramics, with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0, were measured at room temperature. The Raman result shows a dominance of 1:2 ordered structure at all Zn substitution contents. All Raman modes shift to lower frequencies with increasing Zn substitution. Higher Qf value correlates well with narrower width of the breathing Raman mode A_1g(4) and larger relative intensity of 1:2 long-range-ordered mode E_g(2) in BMZT solid solution. First-principle calculation was performed to investigate the electronic structure of 1:2 ordered BMT and Ba(Zn_1/3,Ta_2/3)O₃ (BZT). Covalent bond between Zn and O in BZT is much stronger than that between Mg and O in BMT due to the Zn 3d orbital. Zn substitution for Mg leads to longer and weaker Ta-O bonds, which may be one reason for the variation of Raman spectroscopy and microwave dielectric properties of BMZT system.