Far-Infrared Reflection Spectra of Dielectric Ceramics for Microwave Applications |
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Authors: | Koichi Fukuda Ryozo Kitoh Ikuo Awai |
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Affiliation: | Inorganic Materials Research Laboratory, UBE Industries, Ltd., 1978-5, Kogushi, Ube-city, Yamaguchi 755, Japan;Department of Electrical and Electronic Engineering, Yamaguchi University, Tokiwadai, Ube-city, Yamaguchi 755, Japan |
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Abstract: | Far-infrared reflection spectra of dielectric ceramics, BaSm2Ti5O14, BaTi4O9, and some pcrovskites such as Ba(Zn1/3Nb2/3)O3, have been measured at room temperature using a Fourier transform infrared spectrometer in order to investigate the effect of the crystal structure on the dielectric properties. As for perovskites, Sr(Zn1/3Nb2/3)O3 and Sr(Mg1/3Nb2/3)O3, in which B site ions are ordered, were also measured. Reflectance data were analyzed by means of a factorized form of dielectric functions instead of the classical dispersion theory, and all of the spectra were well fitted. The values of dielectric constants and tan δ calculated from the reflectance data were in good agreement with resonant cavity measurements at 5 GHz. Furthermore, results of this study have shown that the main contribution to the microwave dielectric properties is caused by low-frequency optically active modes located at 50 to about 300 cm?1, and for perovskite structures it is suggested that the ordering of B site ions is significant in obtaining low dielectric losses. |
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