Characterization Andanalysis Of Microstructure And Structural Properties For Ba-base Complex Perovskite Microwave Dielectric Ceramics

Microwave devices usually have large information capacity and the characteristicsof strong orientation and penetrability, therefore, microwave dielectric ceramicshave become one of the key materials in modern communication microwavefrequencies（concentrated at300MHz-30GHz). Microwave capacitors, dielectricantenna and other components in modern communication in the world are mainlymade by them. Now the development trend of mobile communication technology isminiaturization and high frequency, so microwave dielectric ceramics which havehigh dielectric constant and quality factor, low dielectric loss and cheaper pricebecome a new hot spot in recent years.The application ofA(B1/2B1/2)O3andA(B1/3B2/3)O3ceramics has a very gooddevelopment prospect. The special structure characteristics and atomic arrangementmake them have excellent dielectric response performance in the area of microwaveand millimeter. This advantage and their photon vibration characteristic are closelylinked, and the characteristic of sample preparation conditions on the photon researchalso has very important influence. Therefore, based on the research of the microscopicstructure, we can explore new technology under the new formula of performance ofthe ceramics, which lay the foundation for the realization of new type ceramics massapplication.In this article the solid preparation method was used for makingBa(Zn1/3Nb2/3)O3-xCaTiO3（BZN-CT，x=0.0，0.30，0.60，0.75，0.90） and(1-x)Ba(Mg1/3Ta2/3)O3-xBa(Co1/3Nb2/3)O3（BMT-BCN，x=0.0，0.20，0.25，0.30， 0.40） microwave dielectric ceramics. Through different data processing methods ofXRD diffraction, Raman scattering and reflection (FTIR) test data were handled, atthe same time they were compared with the samples of measured dielectric properties.The course of the change of the vibration modes and the relationship between microstructure and properties of the crystal were discussed when Ba2+ions replaced by Ca2+ions in the A-site, Zn2+and Nb5+in B-site replaced by Ti4+and Mg2+and Ta4+inB-site replaced by Co2+and Nb4+, respectively.1. Lattice vibration spectra and structure performance summary ofBa(Zn1/3Nb2/3)O3-xCaTiO3ceramic.1) Comparing the XRD data with JCPDS card get pure BZN ceramic for cubicordered structures. Crystal symmetries decrease with CT concentration. Crystalstructure change from cubic to pseudo-cubic and when x=0.60become hexagonalstructure. The lattice constant and the degree of order also change accordingly. Theordered phases transform from1:1to1:2ordered structure with changing crystalstructures.2) F2g(O) vibration mode split into two modes due to the existence of long-range1:2ordered. Meanwhile，the phonons of A1g(Nb) which related to the1:2structureshow a suddenly shift to high frequency at x=0.60.3) The FWHM values of F2g(O) modes imply a positive trend compared withtanδ values and reach a minimum value at x=0.60. Meanwhile, the FWHM values ofthe F2g(O) phonon modes are inversely correlated with dielectric constant randreach a maximum value at x=0.60. An positive correlation shows between theRaman shifts of Eg(O) and temperature coefficient cof the system. It means thatBZN-CT ceramics have the best dielectric properties when x=0.60.4) According to the group theory analysis, the infrared spectrum of the system isidentified. The analysis of the new polar modes at300cm1and600cm1at x≥0.60and the intensity change of imaginary part of dielectric constant, frequency of peakand the research of dielectric properties are discussed. 2. Lattice vibration spectra and structure performance summary of(1-x)Ba(Mg1/3Ta2/3)O3-xBa(Co1/3Nb2/3)O3ceramic.1) Comparing the XRD data with JCPDS card get BMT-BCN ceramic forhexagonal ordered crystal structure. Crystal symmetries and the degree of orderdecrease with BCN concentration.2) The FWHN values of Eg(O) modes show a positive trend compared withdielectric constant rat x≤0.25and then a negative trend at x≥0.25. The FWHNvalues of F2g(O) and A1g(O) modes are inversely correlated with tan values atx≤0.25and similarly correlated at x≥0.25. Temperature coefficient chas anon-linear variation. It indicates that BMT-BCN ceramic solid solution of crystalstructure and dielectric properties achieve a best level when x=0.25.3) According to the group theory analysis, the infrared spectrum of the system is identified. The intensity of BMT-BCN ceramics infrared spectrum suddenly become smaller at x=0.25and some of the vibration modes even disappear.Eventually samples under this component have better dielectric properties and itconfirms the correctness of the XRD and Raman study conclusion.