Analysis of Infrared Reflection Spectra of (Mg_1−xZn_x)Al₂O₄ Microwave Dielectric Ceramics

Abstract

Infrared reflection spectra of (Mg1−xZnx)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.

Determining the Quality Factor of Dielectric Ceramic Mixtures with Dielectric Constants in the Microwave Frequency Range

“…As the substitution molar ratio increases, the microstructure or the parameters of the original molecular will systemically change. Therefore, the quality factor versus the substitution content is currently attributed to interfacial mismatch 44 , mode vibration 35,58 , phase constitution 45,50 , relative density 46 , grain size 47 , dielectric constant 48 , and crystal structure 59 etc . The interfacial mismatch can be related to grain size which corresponds to the two-dimensional defect leading to the dielectric loss 44 .…”

“…The interfacial mismatch can be related to grain size which corresponds to the two-dimensional defect leading to the dielectric loss 44 . The vibration modes can be determined via the Rama measurement 35,58 . However, this usually sweeps a wide range of frequencies, and once the resonator is accomplished the resonant frequency of the microwave dielectric ceramics is determined.…”

“…Shannon et al . has reported that the dielectric constant can be calculated through the Clausius-Mosotti equation, but the equation requires the molecule or ion with a cubic symmetry 2,32–35 . As a result, only the tendency of dielectric constant variation can be roughly estimated if the molecule or ion with non-cubic symmetry 2,5,35 .…”

“…has reported that the dielectric constant can be calculated through the Clausius-Mosotti equation, but the equation requires the molecule or ion with a cubic symmetry 2,32–35 . As a result, only the tendency of dielectric constant variation can be roughly estimated if the molecule or ion with non-cubic symmetry 2,5,35 . The quality factor change of the ionic substitution is usually attributed to the grain size 20,21,23 , porosity 11,12 , structure 24 , phase evolution 5 , internal strain 2,36–38 , material conductivity 39 and so on.…”

Fabrication and luminescence properties of one-dimensional ZnAl2O4 and ZnAl2O4: A3+ (A=Cr, Eu, Tb) microfibers by electrospinning method

“…2b, which can be attributed to the non-degenerate infrared-active mode and symmetry stretching mode of free nitrate ions [30,31]. When the samples were calcined at 1000 8C, the ZnAl 2 O 4 spinel phase formed in the fibers, and new absorption peaks located at 662, 556 and 498 cm À1 are due to the Al-O stretching mode, Zn-O stretching mode and Al-O bending mode respectively [32][33][34][35]. These three peaks are the characteristic of the regular spinel structure [26].…”