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Hydrothermal And Solid-state Synthesis, Dielectric Properties Of Microwave Ceramic Materials With Low Dielectric Constant

Posted on:2017-05-29Degree:MasterType:Thesis
Country:ChinaCandidate:Z L WangFull Text:PDF
GTID:2271330503993109Subject:Chemical engineering
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As the microwave communication have developed in the direction of higher frequency, people put forward more strict requirements for the microwave dielectric materials with low dielectric constant and high quality factor. In this article, Zn2 Ge O4 nanorods and(1-x)Zn Al2O4-x Zn2 Sn O4 solid solution were prepared through hydrothermal synthesis method and solid-state synthesis method, respectively. The XRD, TEM, SEM, EDS, FT-IR, Raman, fluorescence spectra and network analyzer were used to analyze phase composition, microstructure, crystal growth, dielectric properties, etc. of the samples.(1) Zn2 Ge O4 nano materials were obtained via hydrothermal synthesis, the Zn2 Ge O4 pure phase was acquired when the p H value was 7. The single crystal were nanorods with core-shell structure, and possessed high crystallinity. The synthetic temperature was lower to180℃. The length of the nanorods was 50-100 nm, and the aspect ratio was about 3. The size of the nanorods could be controlled by adjusting the synthetic temperature. Through the two-step reaction, the nanorods that the length was more than 500 nm and the aspect ratio reached 8-10 could be obtained. Zn2 Ge O4 nanorods had no oxygen defect. It had narrow excitation peak during 287293.8nm when the average diameter of crystal was less than 22 nm. Due to quantum confinement effect, photoluminescence excitation and emission peaks red-shifted with the diameter of Zn2 Ge O4 nanorods increasing. When the sintered temperature was 1100℃, Zn2 Ge O4 nanomaterials had excellent microwave dielectric properties: εr = 7.27, Q×f = 34,389 GHz, τf =-30.45 ppm/℃. The densification temperature of Zn2 Ge O4 nanorods was very low, sintered temperature range was wide, the dielectric constant was low and temperature stability was also very high.(2) The(1-x)Zn Al2O4-x Zn2 Sn O4 solid solution was acquired through the solid-phase synthesis. The effect of Sn doping amount on the sintering behavior, phase composition, microstructure and dielectric properties was explored. With the increasing of Sn doping amount, the change of XRD diffraction angle has regularity, and the offset conformed to the Bragg law. The addition of Sn atom was beneficial to crystal growth, improved the density of the ceramic greatly. Especially, when the x value was 0.4,(1-x)Zn Al2O4-x Zn2 Sn O4 solid solution has excellent microwave dielectric properties: εr=8.93(15.28GHz), Q×f= 68,200 GHz, τf =-36.79ppm/℃.
Keywords/Search Tags:hydrothermal synthesis method, solid-phase synthesis method, microwave dielectric ceramic with low dielectric constant, Zn2Ge O4 nanorods, (1-x)Zn Al2O4-x Zn2Sn O4 solid solution
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