Terahertz and infrared spectroscopic study on dielectric properties of Bi₂(Zn_1/3Nb_2/3)₂O₇ for microwave application

Dielectric properties of Bi 2 (Zn 1/3 NB 2/3 ) 2 O 7 (BiZN) ceramic materials have been studied using terahertz (THz) and Fourier transform infrared (FTIR) spectroscopies. Real part of dielectric constant ( ε1 ) characterized by FTIR spectroscopy is around ( ε1 ) IR ≅ 60 in low frequency regime ( f <100 cm^-1 ) and decreases dramatically in the vicinity of lattice vibrational resonance frequencies or wavenumbers, approaching ( ε1 ) IR≅204 in high frequency regimes ( f > 1000 cm^-1 ). Real part of dielectric constant ( ε1 ) characterized by THz spectroscopy is a constant value in 0.100.8 THz regime, ( ε1 ) THz≅68, which is essentially the same as the ε1 value obtained by conventional Hakki-Coleman microwave method. These results reveal that there is no lattice vibrational resonance occurring between THz and microwave (or millimeter wave) frequency regimes. Our results indicate that the low frequency dielectric response of BiZN microwave materials is mainly contributed by the ionic polarization.