Far‐Infrared Reflection Spectra of Dielectric Ceramics for Microwave Applications

Abstract

Far‐infrared reflection spectra of dielectric ceramics, BaSm 2 Ti 5 O 14 , BaTi 4 O 9 , and some pcrovskites such as Ba(Zn 1/3 Nb 2/3 )O 3 , 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(Zn 1/3 Nb 2/3 )O 3 and Sr(Mg 1/3 Nb 2/3 )O 3 , 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.