Extended X-ray absorption fine structure, X-ray diffraction and Raman analysis of nickel-doped Ba(Mg1/3Ta2/3)O3

Raman, X-ray diffraction and extended X-ray absorption fine structure (EXAFS) measurements of xBa(Ni1/3Ta2/3)O3 + (1 − x)Ba(Mg1/3Ta2/3)O3 samples with x = 0–0.03 were performed to reveal the nickel doping effect on the microwave properties. EXAFS result clearly shows that the nickel is located on the Mg lattice site. We also found that, as the nickel concentration increases, microwave dielectric constant decreases with the TaO and NiO bond distances. X-ray diffraction shows that the 1:2 ordered structure is degraded with the increasing of nickel concentration. The stretching phonon of the TaO6 octahedra, that is A1g(O) phonon near 800 cm−1, are strongly correlated to the microwave properties of xBa(Ni1/3Mg2/3)O3 + (1 − x)Ba(Mg1/3Ta2/3)O3 samples. The large Raman shift and the large width of the A1g(O) imply rigid but distorted oxygen octahedral structure, therefore, the effect of nickel doping lowers the dielectric constant and the Q × f value of Ba(Mg1/3Ta2/3)O3 ceramic.