Analysis of Infrared Reflection Spectra of (Mg1−xZnx)Al2O4 Microwave Dielectric Ceramics

Infrared reflection spectra of (Mg_{1− x} Zn _x )Al₂O₄ ceramics were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. According to structure analysis, the losses originating from bend vibration and stretch vibration of the bond between A-site cation and oxygen anion dominated the whole dielectric losses of the spinel ceramics. The coexistence of Mg and Zn deteriorated the intrinsic dielectric properties due to the bond asymmetry thus introduced. The calculated Qf (∼10⁵ GHz) was much higher than the measured ones (∼10⁴ GHz), suggesting that the extrinsic loss was significant. Therefore, the microwave dielectric properties of MgAl₂O₄ and ZnAl₂O₄ could be improved much by microstructure modification, and the little superiority in their solution compared with the end-members was due to microstructure improvement.