Synthesis of BaCu(B2O5) Ceramics and their Effect on the Sintering Temperature and Microwave Dielectric Properties of Ba(Zn1/3Nb2/3)O3Ceramics (original) (raw)
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Advances in Materials Science and Engineering
The present research is devoted to the optimization of the sintering schedule of Ba (Co0.7Zn0.3)1/3Nb2/3O3 (BCZN) dielectric ceramics for microwaves applications. A novel approach to the heat treatment of these ceramics based on the rapid-rate sintering (RRS) technique followed by a lower temperature annealing cycle has been developed. The relationships among the heat treatment process optimization, the structural, microstructural characteristics, and the microwave dielectric properties of the BCZN ceramics were investigated using X-ray diffraction, scanning electron microscopy, energy dispersion analysis, and vector network analysis. The RRS-technique shortens substantially the time required for the elaboration of these components in comparison with conventional sintering techniques and prevents simultaneously the formation of secondary phases as Ba5Nb4O15 and Ba8(Co, Zn) 1Nb6O24 on the surface of the ceramics. All of the sintered and annealed ceramics exhibit a high quality factor...
Ceramics International, 2008
The sintering behavior and dielectric properties of the monoclinic zirconolite-like structure compound Bi 2 (Zn 1/3 Nb 2/3) 2 O 7 (BZN) and Bi 2 (Zn 1/ 3 Nb 2/3Àx V x) 2 O 7 (BZNV, x = 0.001) sintered under air and N 2 atmosphere were investigated. The pure phase were obtained between 810 and 990 8C both for BZN and BZNV ceramics. The substitution of V 2 O 5 and N 2 atmosphere accelerated the densification of ceramics slightly. The influences on microwave dielectric properties from different atmosphere were discussed in this work. The best microwave properties of BZN ceramics were obtained at 900 8C under N 2 atmosphere with e r = 76.1, Q = 850 and Q f = 3260 GHz while the best properties of BZNV ceramics were got at 930 8C under air atmosphere with e r = 76.7, Q = 890 and Q f = 3580 GHz. The temperature coefficient of resonant frequency t f was not obviously influenced by the different atmospheres. For BZN ceramics the t f was À79.8 ppm/8C while t f is À87.5 ppm/8C for BZNV ceramics.
Ceramics International, 2013
The ZnO and V 2 O 5 co-doped Ba 3 Ti 2 (Mg 1/3 Nb 2/3) 2 Nb 4 O 21 (BTMNN-2) microwave dielectric ceramics were successfully prepared via a conventional solid-state reaction method. The effect of the 2 ZnO-V 2 O 5 complex additive on the sintering temperature and microwave dielectric properties was specially investigated. The X-ray diffraction analysis reveals that the BTMNN-2 ceramics doped with 2 ZnO-V 2 O 5 form a single hexagonal structure phase without visible secondary phases. A small amount of 2 ZnO-V 2 O 5 additive can significantly lower the sintering temperature of BTMNN-2 ceramics owing to the formation of a liquid phase in the BTMNN-2 matrix, as clearly evidenced by the SEM micrographs. Meanwhile, the experimental results show that the microwave dielectric properties of the samples were strongly dependent on the densification, crystalline phases, and grain size. The 5 wt% 2 ZnO-V 2 O 5 doped BTMNN-2 ceramics can be sintered at 900 1C and own good microwave dielectric properties of e r ¼47, Q Â f ¼10,500 GHz and t f ¼ 16 ppm/1C, showing a potential for applications in mid-permittivity low temperature co-fired ceramics.
Applied Sciences, 2015
The effects of post-annealing on the crystal structure, microstructure, and microwave dielectric properties for Ba(Co 0.7 Zn 0.3) 1/3 Nb 2/3 O 3 ceramics were investigated. The as-prepared materials were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The microwave dielectric properties are measured at 6 GHz using a network analyzer. Ba 5 Nb 4 O 15 and/or Ba 8 (Co,Zn) 1 Nb 6 O 24 secondary phases were found on the surface according to sintering conditions due to volatilization of some Zn and Co elements. The experimental results show that the beneficial effect of the annealing steps to improved the microwave dielectric properties. Excellent microwave dielectric properties were achieved for the coarse-grained microstructures by a higher sintering temperature and with a shorter holding time followed by annealing steps at lower temperatures with a longer holding time. This improvement can be attributed to 1:2 cation ordering within the crystal, which is taking place during annealing process. The Ba(Co 0.7 Zn 0.3) 1/3 Nb 2/3 O 3 ceramic could be used successfully for realization of dielectric microwave resonators, since it has a high quality factor Q f value of 123,700 GHz, a high dielectric constant ε r value of 34.5 and a temperature coefficient of the resonant frequency τ f of 0 ppm/ ¥ C.
Effect of dopants on microwave dielectric properties of Ba(Zn1/3Nb2/3)O3 ceramics
Journal of the European Ceramic Society, 2007
Ba(Zn 1=3 Ta 2=3 )O 3 (BZT) has been prepared with various amounts of different dopants such as oxides of divalent, trivalent, tetravalent, pentavalent and hexavalent elements. Effect of these dopants on microwave dielectric properties of BZT is investigated. Some of the dopants are found to increase quality factor (Q). Most of the dopants increase the temperature coefficient of resonant frequency ( f ). Annealing undoped BZT increased the order parameter and quality factor. Small amounts of dopants such as that of oxides of Zr, Ga, Cr, Ce, Sn, In, Mn and Sb increased the quality factor. The doped ions substitute for the ordered B ions decreasing the order parameter. Annealing Ga and In doped BZT decreased the Q factor where as it increased for Zr, Cr, Ce, Sn, Mn, Sb doped samples. Doping BZT with Zr, Ga, Cr, Ce, Sn, In, Mn, Sb decreased the order parameter but at the same time increased the quality factor indicating that order parameter alone is a poor indicator of quality factor. The quality factor is found to depend on the dopant ionic radii and dopant concentration. The quality factor increased when the ionic radius of the dopant is close to the ionic radius of the B site ions Zn or Ta.
Journal of Materials Science-materials in Electronics, 2007
Ba(Zn1/3Ta2/3)O3 has been prepared with different dopants that gave best microwave dielectric properties at room temperature. Effects of different dopants on the low temperature microwave dielectric properties of BZT were investigated. With decrease in temperature, loss tangent was found to decrease marginally and then increase at temperatures lower than 100 K. Increase in loss factor at lower temperatures were found to be less for dopants with smaller ionic radii. Dielectric constant was found to be almost independent of temperature. Temperature coefficient of resonant frequency slowly decreased from a positive value to negative value when temperature was lowered. Temperature at which τf becomes zero was found to vary for different dopants. There is a temperature stable region for tanδ, ɛr and τf which varies for different dopants.
Ba(Zn1/3Ta2/3)O3 Ceramics for Microwave and Millimeter-wave Applications
Annals of the New York Academy of Sciences, 2009
The Ba(Zn 1/3 Ta 2/3 )O 3 (BZT) ceramic samples were prepared by solid-state reaction and sintered in the range 1550-1650 • C for 2 h. Several methods-X-ray diffraction (XRD) and scanning electron microscopy (SEM)-were used for structural and morphological characterization. The unit cell distortion and the presence of the secondary phase content were studied by XRD. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was noticed with the increase of the sintering temperature. SEM investigations revealed polyhedral well-faceted grains and large grain size distribution. The dielectric properties in the microwave range were measured at room temperature and at 1 kHz on a large temperature interval (±150 • C). The dielectric parameters were correlated with morphological and structural properties. Ceramic samples were annealed at 1410 • C for 30 h to improve the microwave properties. The dielectric constant of BZT samples measured at 6 GHz and at 1 kHz was between 27 and 28 on the whole temperature range, that is, typical values for BZT material. The temperature coefficient of the resonance frequency at 6 GHz exhibits positive values less than 6 ppm/ • C.
Ceramics International, 2011
Doped hexagonal BaTiO 3 (h-BaTiO 3) ceramics have recently been identified as potential candidates for use in microwave dielectric resonators. However, similar to other common microwave ceramics, doped h-BaTiO 3 ceramics require a sintering temperature higher than 1400 8C. In this study, the effects of Bi 2 O 3 and Li 2 CO 3 on the densification, microstructural evolution and microwave properties of hexagonal 12R-Ba(Ti 0.5 Mn 0.5)O 3 ceramics were examined. Results indicate that Bi 2 O 3 and Li 2 CO 3 are able to effectively reduce the sintering temperature of 12R-Ba(Ti 05 Mn 0.5)O 3 ceramics through liquid phase sintering while retaining the hexagonal structure and the microwave dielectric properties. The best results were obtained for the 12R-Ba(Ti 0.5 Mn 0.5)O 3 with the additions of 5 wt% Bi 2 O 3 sintered at 1200 8C
Microwave dielectric resonators (DRs) based on Ba(B 1/2Nb1/2)O3 [B = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In] complex perovskites have been prepared by conventional solid state ceramic route. The dielectric properties (relative permittivity, εr ; quality factor, Q; and resonant frequency, τf ) of the ceramics have been measured in the frequency range 4–6 GHz using resonance methods. The resonators have relatively high dielectric constant in the range 36–45, high quality factor and small temperature variation of resonant frequency. The dielectric properties are found to depend on the tolerance factor (t), ionic radius (r), and lattice parameter (ap).