Simulation and Measurement of Dielectric Constants of Crystal Alumina and Powder Alumina in Terahertz Waveband

Based on the first principles, the vibration properties of alpha alumina are calculated, and the transverse and longitudinal phonon vibration frequencies and high-frequency dielectric constants are obtained. Based on the dielectric constant theoretical model and the infinite plate reflectivity model, the reflectivity of 300K and 900K are obtained. The reflectivity of crystalline aluminum oxide and aluminum oxide powder tablets with two particle sizes were measured by Fourier time-domain spectral reflectance measurement device. The theoretical results are in good agreement with the experimental results, which shows that the calculation based on the first principle can accurately predict the spectral characteristics of materials, and can provide accurate prediction data for material spectral identification.