Synthesis And Microwave Dielectric Properties Of MgO-GeO₂and ZnO-Al₂O₃-Ga₂O₃Dielectric Ceramics

Microwave dielectric ceramics materials with low dielectric constant （εr） and highquality factor have widely used in wireless communications, radar, etc. So attracted numerousresearchers paid attention to the research and development. In this paper, using solid-statemethod to synthesis the ceramics materials, and characterized with X-ray diffraction（XRD）,scanning electron microscopy（SEM）, EDS, thermogravimetry/differential scanningcalorimetry（TG/DSC） and Network analyzer and so on.Studied the phase composition,microstructure and the relationship with the microwave dielectric properties of the Mg₂GeO₄ceramics and Zn(Al_1-xGa_x)₂O₄solid solution ceramics systerms.1. Synthesis Mg₂GeO₄ceramics by solid-state method. It was found that theOrthorhombic Mg₂GeO₄ceramics has wide sintering temperature, the microwave dielectricproperties at1450°C was: εγ=5.48, Q x f=11,000GHz, τf=-27.6ppm/°C. This materialshad excellence dielectric properties when doped with3.00wt.%of B₂O₃sintering aid at1000°C. The Q x f value was fourth times higher than the pure Mg₂GeO₄ceramics（44,626GHz）, without second phase. The τfvalue was a less negative value and insensitive to thesintering temperature.3.00wt.%B₂O₃-doped ceramics exhibited good microwave propertiesat1250°C: εγ=6.76, Q x f=95,028GHz （15.33GHz）, τf=28.73ppm/°C. The addition ofB₂O₃can improve Mg₂GeO₄ceramics microwave dielectric properties, effectively.2. The spinel structure Zn(Al_1-xGa_x)₂O₄solid solution were prepared by solid-statemethod, with the increase of x value, the system didn’t have the second phase. XRDdiffraction peaks migrated to lower degree, which were agreed with the Bragg equation. WithGa2O3increasing, guiding the directional growth of solid solution, improving the density anddielectric properties. When x=0.8, this material had the highest Q x f value at1450°C, theexcellence dielectric performance was: εγ=10.1, Q x f=76,000GHz （12.992GHz）, τf=-36ppm/°C. When x=0.6, the Q x f values were keep above55,000GHz, during the sinteringtemperature range from1400°C to1500°C, and the dielectric contant（εγ） ranged from9.83to9.85, the τfvalue changed from–30.93ppm/°C to–30.87ppm/°C. It mean that x=0.6wasthe appropriate content of the Zn(Al_1-xGa_x)₂O₄solid solution system.In summary, all of these systems exhibited excellence microwave dielectric properties and could be promising millimeter-wave/microwave ceramics candidate materials. Accordingto the analysis method of phase composition, microstructure analysis, doping amount, amountof solid solution and sintering temperature on the dielectric properties were investigated. Thegerminate and new spinel solid solution at low dielectric constant and high quality in the fieldof microwave dielectric ceramics. Our work provided valuable information for the lowdielectric microwave dielectric ceramics research has certain reference value and guidingsignificance.