Role of Ni and Zr doping on the electrical, optical, magnetic, and structural properties of barium zinc tantalate ceramics

Abstract

Properties of Ni- and Zr-doped Ba(Zn1/3Ta2/3)O3 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)O3 are dominated by discrete internal transitions between Ni2+ 3d orbitals. Absorption from the 3Γ2(F) ground state to 4Γ3(F), 3Γ1(D), 5Γ1(D), 4Γ3(P) excited states occurs at approximately 1.55, 1.75, 2.50, and 2.80 eV, respectively. The ligand field strength of neighboring oxygen ions ranges from about 7300 cm−1 (0.25% Ni) to about 7700 cm−1 (1.0% Ni). A significant increase in the visible continuum background is correlated with increased tan δ. This effect is attributed to point defects in the Ni environment, suggesting that point defects play an important role in microwave loss in practical dielectric material.