Correlation of the phonon characteristics and microwave dielectric properties of the Ba(Mg_1/3Ta_2/3)O₃ materials

The Ba(Mg_1/3Ta_2/3)O₃, BMT, materials possess the highest quality factor (Q × f) in microwave frequency regime among the microwave dielectric materials and can potentially be used for high frequency communication application. To understand the mechanism that determines microwave dielectric properties of the BMT materials, spectroscopic techniques including Raman and Fourier transform infrared (FTIR) analyses are used for investigating the phonon characteristics of the materials. The Raman-shift (Δω_0j) of the Raman peaks and the resonance frequency (ω_0j) of the FTIR peaks vary insignificantly among the samples, which correlate very well with the phenomenon that the K-values for these materials are similar with one another. In contrast, the full-width-at-half-maximum (FWHM) of the Raman peaks and the damping coefficient (γ_j) of the FTIR peaks vary markedly among the samples. The high-Q materials possess sharpest vibrational modes, viz., smallest FWHM value for Raman peaks and smallest γ_j value for FTIR peaks and vice versa. The intimate relationship between the phonon characteristics and the fine structure of the materials is confirmed.