G. Rong et al., Role of Ni and Zr doping on the electrical, optical, magnetic, and structural properties of barium zinc tantalate ceramics, J MATER RES, 14(10), 1999, pp. 4011-4019
Properties of Ni- and Zr-doped Ba(Zn1/3Ta2/3)O-3 ceramics are reported. The
nickel ion has an effective paramagnetic moment of 3.22 +/- 0.05. Optical
spectra of Ni-doped Ba(Zn1/3Ta2/3)O-3 are dominated by discrete internal tr
ansitions between Ni2+ 3d orbitals. Absorption from the (3)Gamma(2)(F) grou
nd state to (4)Gamma(3)(F), (3)Gamma(1)(D), (5)Gamma(1)(D), (4)Gamma(3)(P)
excited states occurs at approximately 1.55, 1.75, 2.50, and 2.80 eV, respe
ctively. The Ligand field strength of neighboring oxygen ions ranges from a
bout 7300 cm(-1) (0.25% Ni) to about 7700 cm(-1) (1.0% Ni). A significant i
ncrease in the visible continuum background is correlated with increased ta
n delta. This effect is attributed to point defects in the Ni environment,
suggesting that point defects play an important role in microwave loss in p
ractical dielectric material.