Study On The Preparation And Microwave Dielectric Properties Of Medium And Low Dielectric Microwave Dielectric Ceramics

In order to obtain high quality factor,near-zero temperature coefficient of the resonant frequency and low sintering temperature ceramics,a serials of microwave dielectric materials with good microwave dielectric properties were prepared by adding oxides with low melting point,doping trace elements and adjusting composition.(1)The Mg2Al4Si5O18+xwt%BaCu(B2O5)(15?x?30)ceramics were prepared via the solid-state reaction method.The XRD patterns shows that samples are composed of Mg2Al4Si5O18 and BaAl2Si2Os.The phase structure for BaA12Si2Os ceramic changed from hexagonal phase to monoclinic phase,with the increase of sintering temperature and BCB.The optimized sintering temperature of Mg2Al4Si5O18 ceramics was reduced to 900? by adding 30wt%BCB.After sintering 900 ? for 4h,Mg2Al4Si5O18+30wt%BCB ceramics exhibited good microwave dielectric properties with ?r=3.4,Q×f=21334 GHz and ?f=-30ppm/? sintered at 900? for 4h,indicating that it is a candidate for LTCC devices.(2)The BaLa4Ti4O15+1 wt%M(M=GeO2?MnO2)ceramics were prepared by the solid-state reaction method.The XRD diffraction pattern shows that the diffraction peak of the test sample corresponds to the diffraction peak of BaLa4Ti4O15,and no second phase was detected.The best sintering condition of BaLa4Ti4O15+1wt%M(M=GeO2?MnO2)ceramics was 1475 0C for 6h.Under this optimum sintering temperature condition,the microwave dielectric properties of ceramics were obtained:?r=42.3,Q×f=21120 GHz,?f=-1.6 ppm/? for BaLa4Ti4O15+1wt%GeO2 ceramics,and ?r=44.3,Q×f=8620 GHz,?f=0.62 ppm/?for BaLa4Ti4O15+1wt%MnO2.(3)The BaLa4Ti4O15+xwt%SrTiO3(x=1?4)ceramics were prepared by the solid-state reaction method.The XRD patterns show that a single phase of BaLa4Ti4O15 was formed as the addition content SrTiO3 was 1wt%.The second phase(Ba0.256 Sr0.744)TiO3 was formed with increasing the content of SrTiO3.The content of the second phase increased with the increase of SrTiO3 content.Due to the existence of the two phases,with adding SrTiO3,the quality factor value of ceramics was decreased and the temperature coefficient of the resonant frequency was not adjusted to near zero.After sintering at 1500? for 6h,BaLa4Ti4O15+1wt%SrTiO3 ceramics have good microwave dielectric properties with ?r=46.5,Q×f=41539 GHz,?f=-5.3ppm/?.(4)The BaNd4Ti4O15 and BaSm4Ti4O15 ceramics were prepared by the solid-state reaction method.The XRD patterns show that,the BaNd4Ti4O15 ceramic is composed of the phases of BaNd2Ti3O10?BaTi4O9?Nd2TiO5 and the BaSm4Ti4O15 ceramic is composed of the phases of BaSm2Ti3O10?BaTi4O9?Sm2TiO5.The optimized sintering condition is1500? for 6h.After sintering at 1500? for 6h the good microwave dielectric properties were obtained:?r=31.6,Q×f=27500GHz,?f=56.3 ppm/0C for BaNd4Ti4O15 ceramics,and ?r=32.6,Q×f=21800GHz,?f=96.8 ppm/? for BaSm4Ti4O15 ceramics.(5)The 0.69CaTiO3-0.31SmAlo3+xwt%CeO2(x=0.5,1,1.5,2)ceramics were prepared by the solid-state reaction method.The XRD patterns show that,the 0.69CaTiO3-0.31SmAlO3+xwt%CeO2(x=0.5,1,1.5,2)ceramics could form a solid solution with similar structure to CaTiO3,without the generation of second phase.The microwave dielectric properties of 0.69CaTiO3-0.31 SmAlO3+1w%CeO2 ceramics sintered at 1500 ? for 6h were obtained:?r=42.7,Q×f=43612GHz,?f=-6.46 ppm/?.