摘要
The structures of Ta O6 and Nb O6 oxygen octahedra in xBa (Mg13 Ta23) O3 + (1-x) Ba (Mg13 Nb23) O3 perovskite ceramics with x=0, 0.25, 0.50, 0.75, and 1.0 were investigated by the extended x-ray absorption fine structure method. The decline in the microwave dielectric constant as x increases is caused mainly by the decrease of the mean volume of the oxygen octahedra, regardless of the 1:2 ordered structure and the distortion of the oxygen octahedron. The low Qf values of the Ta O6 and Nb O6 mixed samples are caused by not only the degrading of the 1:2 ordered structure but also the distortion of oxygen octahedral cages. © 2006 American Institute of Physics.