| Nowadays,microwave technology is mainly used in communication,radar,environmental remote sensing and medical systems.However,the high frequency and short wave length of microwave energy make it difficult to analyze and design microwave components and modules,but microwave dielectric ceramics can be well adapted to the miniaturization development and innovation of microwave system.Microwave ceramics,which full name is microwave dielectric ceramics,are one of the hotspots of research at home and abroad.Microwave dielectric ceramics can not only has good mechanical properties and chemical stability,but also reducing the size of the device because of its high?r;reducing device lossb ecause of its high Q×f,making device be temperature stable because of its near zerof.Microwave dielectric ceramics are widely used in microwave communication systems'components such as resonator,filter,oscillator capacitor,waveguide circuit,antenna substrate etc.Therefore,the research on microwave dielectric ceramics with low cost and better performance is the key to the development of microwave field.Microwave dielectric ceramic samples in this thesis ues the traditional solid state sintering method.Li2Zn3Ti4O12 is the main phase of this research,then analysed the phase composition,microstructure and dielectric properties of nonstoichiometric Zn element and Li element,LiF doped and calcium doped ceramic materials.And the main researchs results are as followings:1.The lower sintering temperature of Li2Zn3Ti4O12 microwave ceramic material can it used in the LTCC manufacturing technology.When the doping amount of LiF increases,LiF phase was observed.LiF and Li2Zn3Ti4O12 didn't reaction,when the doping amount of LiF was 1wt.%,the ceramic can be well sintered at 900?,ehhibited the best comprehensive properties of:?r=17.9,Q×f=47983 GHz,?f=-48.3 ppm/?.2.In order to adjust thef of Li2Zn3Ti4O12 ceramic to near zero,(Li2Zn3-xTi4-xO12-3x)-xCaTiO3?x=0.00-0.32?microwave dielectric ceramics were prepared.The LZT and CaTiO3 co-ehisted with each other and formed a stable composite system when the calcium was added.The calcium ions didn't substite zinc ions When the h value increased from 0 to 0.32,thef increases from-48 ppm/?to 9.12 ppm/?.For x=0.28,the(Li2Zn3-xTi4-xO12-3x)-xCaTiO3 ceramics sintered at 1200°C for 4 h ehhibited ehcellent comprehensive properties of?r=23.5,Q×f=55604 GHz and?f=0 ppm/?.3.In order to obtain ceramic materials with better dielectric properties,the ffects of nonstoichiometric Zn element and Li element as Li2Zn3Ti4O12.Li2Zn3-x-x Ti4O12-x?x=0.00-0.50?and Li2-xZn3Ti4O12-0.5x?x=-0.20-0.20?microwave dielectric ceramics were prepared by the solid state react method.When the x value of Li2Zn3-x-x Ti4O12-x material increased from 0 to 0.50,the ceramics were always single-phase structure.When x=0.30,Li2Zn3-xTi4O12-x ceramic material sintered at 1200°C for 4h ehhibited the best microwave dielectric properties of:?r=21,Q×f=64951 GHz and?f=42.3 ppm/°C.In Li2-xZn3Ti4O12-0.5x?x=-0.200.20?dielectric ceramics,when the value of x increased from-0.20 to 0.20,the Li2ZnTi3O8 phases and a small amount of impurity phases were.obversed.The?f of ceramic was improved from-48.3 ppm/°C to-20.4 ppm/°C.When x=0.15,Li2-x-x Zn3Ti4O12-0.5x ceramic material sintered at 1200°C for 4 h had the best microwave dielectric properties of:?r=20.3,Q×f=68817 GHz and?f=-25.7 ppm/°C. |
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