Characterization And Analysis Of Microstructure For Ba-base Complex Perovskite Microwave Dielectric Ceramics

For the exhibit excellent microwave dielectric properties that complex perovskitemicrowave dielectric ceramics have, such as high values of dielectric constant, highquality factor, near zero temperature coefficient of the resonant frequency and so on,they are widely used in harmonic oscillator, mobile communications, and satellitecommunications. This kind of functional ceramic materials good temperature stability,the advantages of small volume, light quality, cheaper price is one of the reasons wereceived. Therefore, in recent years, the research of microwave dielectric ceramicsbecome a new hot spot.A (B ’1/2B "1/2) O3and A(B’1/3B”2/3)O3ceramics is one of the microwavedielectric materials application prospect widely. The intrinsic properties of microwavedielectric ceramics show that in the dielectric material, atomic thermal vibration nearthe equilibrium position and its closely related to dielectric properties, so the thermalvibration of microwave dielectric ceramics () of lattice vibration properties of theoryresearch and doping modification research, to study the cause of the microwavedielectric material properties and the influence factors to provide importantinformation.TheBa[Mg(1-x)/3ZrxNb2(1-x)/3]O3(BMZN, x=0.0,0.05,0.1,0.2), andBa[Mg(1-x)/3ZrxTa2(1-x)/3]O3(BMZT, x=0.0,0.05,0.1,0.2,0.3) solid solution ceramicswere synthesized by the conventional solid-state sintering technique. Vibrationspectra (Raman spectroscopy and Fourier transform far-infrared reflectionspectroscopy, short for FTIR) and X-ray diffraction (XRD) were employed toevaluate the correlation between crystal structures and vibration modes of these solid solutions replaced by Zr4+ions in the B-site. As well as to identify vibration modeand the relationship between the vibration mode.Vibration spectra and structural characters of Ba[Mg(1-x)/3ZrxNb2(1-x)/3]O3ceramic.1) Cubic crystal structure of the BMZN ceramics is studied by X-ray diffractionand the lattice constants (a) increase with the increasing Zr4+ions, while the dielectricconstants increase accordingly. BMZN Solid solution of symmetry, the cubic phaseshift from the six parties, ordered structures of BMN1:2ordered to1:1and orderly.2)For BMZN ceramics, oxygen octahedron distortion occurs where x=0.05, andthe ordered phase changes from1:2of BMN to1:1of BMZN.3) The dielectric constants have positive correlation with the FWHM values ofthe A1g(O) phonon modes and the Raman shifts of A1g(Nb) modes and have aninverse correlation with the Raman shifts of the A1g(O) phonon modes. Thetemperature coefficients of capacitance have an inverse correlation with the Ramanshifts of A1g(Nb) modes, and the dielectric losses have an inverse correlation with theFWHM values of A1g(Nb) modes.Structure characteristics, Raman, infrared vibrational spectrum and dielectricproperties of Ba[Mg(1-x)/3ZrxTa2(1-x)/3]O3Ceramic solid solution.For the BMZN ceramics, with the increase in the Zr4+content, the latticestructure of ceramics turns gradually from disordered cubic structure to orderedstructure and antiphase tilting of the oxygen octahedra occurs, which is the mainreason for phase transition and variation of crystal structure. from hexagonal (P3m1)to pseudocubic (I4/mcm)and next to cubic (Pm3m).The crystal structures and dielectric properties of the BMZT microwavedielectric ceramics synthesized via solid-state reaction method were characterized byXRD and Raman, and their relationships between the Raman modes, the crystalstructures and dielectric properties were systematically studied. The addition of BaZrO3has an important effect on the crystal structures and dielectric properties ofBMZT ceramics. The symmetry of BMZT solid solution is improved and the crystalstructures are converted from a hexagonal structure to a cubic structure withincreasing Zr4+content. Moreover, the ordered phases are transformed from the1:2ordered structure,to the1:1ordered structure.3) The A1g(O) mode is the vibrational mode with the highest intensity and isrelated to the oxygen octahedron vibration of the ordered phase. In short, the degreeof order decreases with increasing Zr4+content. The Raman shifts of the A1g(O)modes have a positive correlation with the temperature coefficients of constant from x=0to x=0.30and also a positive correlation with the dielectric constants, as well asan inverse correlation with the dielectric constants and the dielectric losses.