K. Fukuda et al., FAR-INFRARED REFLECTION SPECTRA OF DIELECTRIC CERAMICS FOR MICROWAVE APPLICATIONS, Journal of the American Ceramic Society, 77(1), 1994, pp. 149-154
Far-infrared reflection spectra of dielectric ceramics, BaSm2Ti5O14, B
aTi4O9, and some perovskites such as Ba(Zn1/3Nb2/3)O3, have been measu
red at room temperature using a Fourier transform infrared spectromete
r in order to investigate the effect of the crystal structure on the d
ielectric 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. Refle
ctance data were analyzed by means of a factorized form of dielectric
functions instead of the classical dispersion theory, and all of the s
pectra were well fitted. The values of dielectric constants and tan de
lta calculated from the reflectance data were in good agreement with r
esonant cavity measurements at 5 GHz. Furthermore, results of this stu
dy have shown that the main contribution to the microwave dielectric p
roperties is caused by low-frequency optically active modes located at
50 to about 300 cm-1, and for perovskite structures it is suggested t
hat the ordering of B site ions is significant in obtaining low dielec
tric losses.