Microwave dielectric properties of Ba[(Zn1-xCox) 1/3Nb2/3]O3 ceramics

Microwave dielectric ceramics of Ba[(Zn1 - xCOx)(1/3)Nb-2/3]O-3 (x=0-0.8) were prepared by solid-state reaction method. The microwave dielectric properties, such as dielectric constants, Q x f values and tau(f) (temperature coefficient of resonant frequency) were studied as a function of compositions and sintering temperatures. The results revealed that the dielectric constant and Q x f value decrease almost linearly with increasing x. With x increasing from 0 to 0.8, the dielectric constant decreases from 42 to 33, and Q x f value from 75,491 to 20,248 GHz. A nearly zero tau(f) ceramic with dielectric constant of 33 and Q x f value of 20,248 GHz was obtained at x = 0.8. The sintering temperature has slight effect on dielectric constant, but significant on Q x f value. The microstructures and crystal structures were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis techniques to reveal the mechanisms. (C) 2004 Elsevier B.V. All rights reserved.