Sintering behavior and microwave dielectric properties of Bi2O3–ZnO–Nb2O5-based ceramics sintered under air and N2 atmosphere (original) (raw)
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Journal of the American Ceramic Society, 2006
BaCu(B 2 O 5) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B 2 O 5) phase was formed at 7001C and melted above 8501C. The BaCu(B 2 O 5) ceramic sintered at 8101C had a dielectric constant (e r) of 7.4, a quality factor (Q Â f) of 50 000 GHz and a temperature coefficient of resonance frequency (s f) of À32 ppm/1C. As the BaCu(B 2 O 5) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B 2 O 5) was added to the Ba(Zn 1/3 Nb 2/3)O 3 (BZN) ceramic, BZN ceramics were well sintered even at 8501C. BaCu(B 2 O 5) existed as a liquid phase during the sintering and assisted the densification of the BZN ceramic. Good microwave dielectric properties of Q Â f 5 16 000 GHz, e r 5 35, and s f 5 22.1 ppm/1C were obtained for the BZN16.0 mol% BaCu(B 2 O 5) ceramic sintered at 8751C for 2 h.
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.
Microwave Dielectric Properties of Nb2O3-Zn0.95Mg0.05TiO3+0.25TiO2 Ceramics with Bi2O3 Addition
Jiang/Ceramic, 2010
The effects of Bi 2 O 3 addition on the microwave dielectric properties and the microstructures of Nb 2 O 5 -Zn 0.95 Mg 0.05 TiO 3 + 0.25TiO 2 (Nb-ZMT ) ceramics prepared by conventional solid-state routes have been investigated. The results of X-ray diffraction (XRD) indicate the presence of four crystalline phases, ZnTiO 3 , TiO 2 , Bi 2 Ti 2 O 7 , and (Bi 1.5 Zn 0.5 )(Ti 1.5 Nb 0.5 )O 7 in the sintered ceramics, depending upon the amount of Bi 2 O 3 addition. In addition, in order to confirm the existence of (Bi 1.5 Zn 0.5 )(Ti 1.5 Nb 0.5 )O 7 phase in the samples, the microstructure of Nb-ZMT ceramic with 5 wt.% B 2 O 3 addition was analyzed by using a transmission electron micrograph. The dielectric constant of Nb-ZMT samples was higher than ZMT ceramics. The Nb-ZMT ceramic with 5 wt.% Bi 2 O 3 addition exhibits the optimum dielectric properties: Q × f = 12,000 GHz, ε r = 30, and τ f = −12 ppm/ • C. Unlike the ZMT ceramic sintered at 900 • C, the Nb-ZMT ceramics show higher Q value and dielectric constant. Moreover, there is no Zn 2 TiO 4 existence at 960 • C sintering. To understand the co-sinterability between silver electrodes and the Nb-ZMT dielectrics, the multilayer samples are prepared by multilayer thick film processing. The co-sinterability (900 • C) between silver electrode and Nb-ZMT dielectric are well compatible, because there are no cracks, delaminations, and deformations in multilayer specimens.
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...
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.
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.
The 0.83ZnAl2O4-0.17TiO2 (ZAT) ceramics were synthesized by solid state ceramic route. The effect of 27B2O3-35Bi2O3- 6SiO2-32ZnO (BBSZ) glass on the microwave dielectric properties of ZAT was investigated. The crystal structure and the microstructure of the ceramic-glass composites were studied by X-ray diffraction and scanning electron microscopic techniques. The low frequency dielectric loss was measured at 1 MHz. The dielectric properties of the sintered samples were measured in the microwave frequency range by the resonance method. Addition of 0.2 wt% of BBSZ improved the dielectric properties with quality factor (Qu f) > 120,000 GHz, temperature coefficient of resonant frequency (tf) = 7.3 ppm/8C and dielectric constant (er) = 11.7. Addition of 10 wt% of BBSZ lowered the sintering temperature to about 950 8C with Qu f > 10,000 GHz, er = 10 and tf = 23 ppm/8C. The reactivity of 10 wt% BBSZ added ZAT with silver was also studied. The results show that ZAT doped with suitable amount of BBSZ glass is a possible material for low-temperature co-fired ceramic (LTCC) application
Microwave Dielectric Properties of Bi2O3-TiO2 Composite Ceramics
Bi2O3-TiO2 composite dielectric ceramics have been prepared by a conventional solid state ceramic route. The composite ceramics were prepared with starting materials of different origin and the microwave dielectric properties were investigated. The sintered ceramics were characterised by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, Raman and microwave methods. Structural and microstructural analyses identified two separate phases: TiO2 (rutile) and Bi2Ti4O11. The separate grains of titania and bismuth titanate were distributed uniformly in the ceramic matrix. The composition 0.88TiO2-0.12Bi2Ti4O11 was found to have a Q´f of 9,300 GHz (measured at a frequency of 3.9 GHz), a temperature coefficient of frequency, tcf, near zero and a high relative permittivity, er, of 83. The microwave dielectric properties were measured down to 20oK K. The quality factor increased on cooling the ceramic samples. Key words : Dielectric ceramics, Microwave material, Bismuthtitanate, Bi2O3, TiO2