Structure and Dielectric Properties of Citrate Sol-Gel Derived Microwave Ceramics in CaO-ZnO-TiO2 System
Microwave dielectric ceramics of CaO-2ZnO-xTiO2 (x=6~9) were prepared by citrate sol-gel method. The phase formation and structural properties of the ceramics were investigated as a function of titania content (x). Monophase of Ca2Zn4Ti16O38 polytitanates were formed at x = 8. With the increase of x, residual rutile phase were observed, whereas with the decrease of x, the CaTiO3 and Zn2TiO4 phases were detected. The microwave dielectric properties of the sintered ceramics were investigated using resonance method. The variation of dielectric properties of the ceramics as a function of titania content (x) was investigated. For the monophase of Ca2Zn4Ti16O38 polytitanate at x = 8, the dielectric properties showed minimum dielectric constant of 48.1, minimum temperature coefficient of resonant frequencies +44.1 ppm/oC, and maximum Q×f value of 31000 (at 6.921GHz). Deviating from x = 8, the dielectric constant and temperature coefficient of resonant frequencies slightly increased, and the Q×f value decreased. The variation was concerned with the presence of secondary phase.
Wei Pan and Jianghong Gong
F. Zhao, Z. X. Yue, J. Pei, Z. L. Gui, L. T. Li, "Structure and Dielectric Properties of Citrate Sol-Gel Derived Microwave Ceramics in CaO-ZnO-TiO2 System", Key Engineering Materials, Vols. 336-338, pp. 304-306, 2007