Investigation On The Structure And Properties Of Regulation In Magnesium Aluminum Silicate Microwave Dielectric Ceramics

Low dielectric constant microwave dielectric ceramics are widely used in communication systems,which promote a extensive and in-depth research in this kind of material.Magnesium aluminum silicates with lower dielectric constant are getting more attention,while the loss,temperature drift coefficient is larger and these shortcomings seriously affect their scope of application.Therefore,it is possible to change the microwave dielectric properties by controlling the micro structure of the material and the adjustment of the macro structure.Cordierite ceramic(Mg2Al4Si5O18)is a kind of typical low dielectric ceramic because of its special internal and external six membered ring structure with strong adjustability.In this paper,by adding corresponding stoichiometric TiO2 in the raw materials of synthesizing cordierite,Mg2Al4Si5-xTixO18 and Mg2Al4-xTixSi5O18+0.5x of two kinds of different substances are assumed to be made.The compounds are analyzed by X-ray diffraction(XRD),both of them are Mg2Al4(Si5-xTix)O18,and the best microwave dielectric properties for these ceramics are:?r=6.4,.Qf=75000GHz,?f=-5ppm/?(x=0.30).Cordierite internal six membered ring structure are changed directly with the incorporation of TiO2 while adding Ln2O3(Ln=La,SM)alter cordierite external six membered ring structure.Using XRD and Raman spectroscopy,the differences of cordierites Cccm structure are gotten.The Ln3+ substitution of Mg2+in the external six membered ring pull the internal six membered ring to change its symmetry,the minimum of the loss in the ceramic series is(Mg1-xLax)2Al4Si5O18+x(x=0.05)solid solution ceramics:?r=6.7,Qf=78,500(@14.3 GHz)and ?f=22 ppm/?;the best temperature stability is the(Mg1-xSmx)2Al4Si5O18+x(x=0.20)ceramic:?r=6.8,Qf=24,8 00GHz(@13.2 GHz),?f=17 ppm/?.Mg2SiO4 ceramic is also widely used as a kind of low dielectric ceramics because of its lower loss.In this paper,the resonant frequency temperature drift coefficient of the resonator is adjusted by adding the Ti02 layer to change the macroscopic physical structure.Finally,when the TiO2 layer and Mg2SiO4 layer height ratio are close to 1:6,the multilayer ceramic temperature drift coefficient(?f)is near zero.However,their Qf value are very low.In the above experiments,accurate determinations of the microwave properties of samples are needed.So in this article,the design and production of the classic open cavity microwave dielectric properties tester can facilitate the measurement of the dielectric resonator resonant frequency,dielectric constant and loss.