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1.
《Ceramics International》2017,43(4):3688-3692
Li2O-3MgO-mTiO2 (1≤m≤6) ceramics were prepared by the solid state reaction method. X-ray diffraction, energy dispersive spectrometer and scanning electron microscopy techniques were used to investigate the phase composition and crystal structure. With increasing m values, the phase structures of ceramics changed as: (Li2Mg3TiO6, m=1)→(Li2Mg3Ti4O12 and Mg2TiO4, m=2,3)→(Li2Mg3Ti4O12, m=4)→(Li2Mg3Ti4O12, MgTiO3 and Li2MgTi3O8, m=5)→(Li2Mg3Ti4O12, MgTiO3, Li2MgTi3O8 and MgTi2O5, m=6). The optimized sintering temperature was lowered from 1275 °C to 1050 °C. When m=5, Li2O-3MgO-5TiO2 ceramics showed good microwave dielectric properties at a wide sintering temperature range of 1000–1200 °C, and the best microwave dielectric properties of Q×f=71,726 GHz, εr=21.9 and τf=−20.9 ppm/°C were obtained at a relatively low sintering temperature of 1050 °C. 相似文献
2.
《Ceramics International》2016,42(7):7962-7967
Y2O3 ceramics with good dielectric properties were prepared via co-precipitation reaction and subsequent sintering in a muffle furnace. The effects of Nd doping and sintering temperature on microwave dielectric properties were studied. With the increase in sintering temperature, the density, quality factor (Q×f), and dielectric constant (εr) values of pure Y2O3 ceramics increased to the maximum and then gradually decreased. The Y2O3 ceramics sintered at 1500 °C for 4 h showed optimal dielectric properties: εr=10.76, Q×f=82, 188 GHz, and τf=−54.4 ppm/°C. With the addition of Nd dopant, the Q×f values, εr, and τf of the Nd: Y2O3 ceramics apparently increased, but excessive amount degraded the quality factor. The Y2O3 ceramics with 2 at% Nd2O3 sintered at 1460 °C displayed good microwave dielectric properties: εr=10.4, Q×f=94, 149 GHz and τf=−46.2 ppm/°C. 相似文献
3.
Q.J. Mei C.Y. Li J.D. Guo S.X. Huang X.H. Zhang H.T. Wu 《Ceramics International》2013,39(8):9145-9149
Microwave dielectric properties of corundum-structured Mg4Ta2O9 ceramics were investigated as a function of sintering temperatures by an aqueous sol–gel process. Crystal structure and microstructure were examined by X-ray diffraction (XRD) technique and field emission scanning electron microscopy (FE-SEM). Sintering characteristics and microwave dielectric properties of Mg4Ta2O9 ceramics were studied as a function of sintering temperature from 1250 °C to 1450 °C. With increasing sintering temperature, the density, εr and Qf values increased, saturating at 1300 °C with excellent microwave properties of εr=11.9, Qf=195,000 GHz and τf=?47 ppm/°C. Evaluation of dielectric properties of Mg4Ta2O9 ceramics were also analyzed by means of first principle calculation method and ionic polarizability theory. 相似文献
4.
《Ceramics International》2017,43(2):2246-2251
Ultrahigh-Q Li2(1+x)Mg3ZrO6 microwave dielectric ceramics were successfully prepared by means of atmosphere-controlled sintering through simultaneously adopting double crucibles and sacrificial powder. This technique played an effective role in suppressing the lithium volatilization and further promoting the formation of the liquid phase, as evidenced by the X-ray diffraction, microstructural observation and the density measurement. Both dense and even microstructure, and the suppression of detrimental secondary phases contributed to low-loss microwave dielectric ceramics with Q×f values of 150,000–300,000 GHz. Particularly, desirable microwave dielectric properties of εr=12.8, Q×f=307,319 GHz (@9.88 GHz), and τf=−35 ppm/°C were achieved in the x=0.06 sample as sintered at 1275 °C for 6 h. 相似文献
5.
《Ceramics International》2016,42(9):11003-11009
A low temperature sintering method was used to avoid the relatively high sintering temperatures typically required to prepare 0.67CaTiO3–0.33LaAlO3 (CTLA) ceramics. Additionally, CeO2 was introduced into the CTLA ceramics as an oxygen-storage material to improve their microwave dielectric properties. 0.67CaTiO3–0.33LaAlO3 ceramics co-doped with B2O3–Li2O–Al2O3 and CeO2 were prepared by a conventional two-step solid-state reaction process. The sintering behavior, crystal structure, surface morphology, and microwave dielectric proprieties of the prepared ceramic samples were studied, and the reaction mechanism of CeO2 was elucidated. CTLA+0.05 wt% BLA+3 wt% CeO2 ceramics sintered at 1360 °C for 4 h exhibited the optimal microwave dielectric properties: dielectric constant (εr)=45.02, quality factor (Q×f)=43102 GHz, and temperature coefficient of resonant frequency (τf)=2.1 ppm/°C. The successful preparation of high-performance microwave dielectric ceramics provides a direction for the future development and commercialization of CTLA ceramics. 相似文献
6.
《Ceramics International》2016,42(7):7943-7949
This paper reports the investigation of the performance of Li2O–B2O3–SiO2 (LBS) glass as a sintering aid to lower the sintering temperature of BaO–0.15ZnO–4TiO2 (BZT) ceramics, as well as the detailed study on the sintering behavior, phase evolution, microstructure and microwave dielectric properties of the resulting BZT ceramics. The addition of LBS glass significantly lowers the sintering temperature of the BZT ceramics from 1150 °C to 875–925 °C. Small amount of LBS glass promotes the densification of BZT ceramic and improves the dielectric properties. However, excessive LBS addition leads to the precipitation of glass phase and growth of abnormal grain, deteriorating the dielectric properties of the BZT ceramic. The BZT ceramic with 5 wt% LBS addition sintered at 900 °C shows excellent microwave dielectric properties: εr=27.88, Q×f=14,795 GHz. 相似文献
7.
This study elucidates the microwave dielectric properties and microstructures of Nd(Mg0.5Sn0.5?xTix)O3 ceramics with a view to their potential for microwave devices. The Nd(Mg0.5Sn0.5?xTix)O3 ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the Nd(Mg0.5Sn0.4Ti0.1)O3 ceramics revealed no significant variation of phase with sintering temperatures. A dielectric constant (?r) of 21.1, a quality factor (Q × f) of 50,000 GHz, and a temperature coefficient of resonant frequency (τf) of ?60 ppm/°C were obtained for Nd(Mg0.5Sn0.4Ti0.1)O3 ceramics that were sintered at 1550 °C for 4 h. 相似文献
8.
《Ceramics International》2016,42(14):15242-15246
In this work, 0.86CaWO4–0.14Li2TiO3 ceramics were prepared via a traditional solid-state process. The effects of Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) addition on the phase formation, sintering character, microstructure and microwave dielectric properties of the ceramics were investigated. A small amount of LBSCA addition could effectively lower the sintering temperature of the ceramics. X-ray diffraction analysis revealed that CaWO4 and Li2TiO3 phases coexisted without producing any other crystal phases in the sintered ceramics. The dielectric constant and Qf values were related to the amount of LBSCA addition and sintering temperatures. All specimens could obtain near-zero temperature coefficient (τf) values through the compensation of the positive τf of Li2TiO3 and the negative τf of CaWO4. The 0.86CaWO4–0.14Li2TiO3 ceramic with 0.5 wt% LBSCA addition and sintered at 900 °C for 3 h exhibited excellent microwave dielectric properties of εr=12.43, Qf=76,000 GHz and τf=−2.9 ppm/°C. 相似文献
9.
《Journal of the European Ceramic Society》2023,43(8):3331-3337
Low temperature sintered Li8MgxTi3O9+xF2 microwave dielectric ceramics with x = 2−7 were developed based on a newly designed pseudo ternary phase diagram of the Li2TiO3–MgO–LiF system. Dense solid solution ceramics (of relative density >96 %) with cubic rock-salt structure, accompanied by a small amount of secondary phase MgO, were obtained in the temperature range of 800−925 °C. With increasing Mg2+ content, the value of εr decreased, whereas that of τf remained nearly constant, and the Q × f increased to a maximum at x = 5. The Li8Mg5Ti3O14F2 ceramic sintered at 875 °C exhibited superior microwave dielectric properties with εr = 16.8, Q × f = 119,700 GHz, and τf = −41.6 ppm/°C. The good compatibility with Ag electrodes highlights the promising prospects of this ceramic in low-temperature co-fired ceramic technology. Furthermore, a dielectric resonator antenna fabricated based on a Li8Mg5Ti3O14F2 ceramic exhibited an outstanding S11 of −34.7 dB and a broad bandwidth of 360 MHz at the desired resonant frequency of 5.98 GHz. 相似文献
10.
《Ceramics International》2016,42(16):18333-18337
The effect of CuO/MnO additives on phase composition, microstructures, sintering behavior, and microwave dielectric properties of 3ZrO2-3TiO2-ZnNb2O6 (3Z-3T-ZN) ceramics prepared by conventional solid-state route were systematically investigated. CuO/MnO doped ceramics exhibited a main phase of α-PbO2-structured ZrTi2O6 and a secondary phase of rutile TiO2. SEM results showed that the grain size of MnO doped ceramics became larger with increasing amount of dopants. The presence of CuO/MnO additives effectively reduced the sintering temperature of 3Z-3T-ZN ceramics to 1220 °C. MnO doped into ceramics could enhance the Q×f values significantly. The 0.5 wt% CuO doped 3Z-3T-ZN ceramics with 0.5 wt% of MnO, sintered at 1220 °C for 4 h, was measured to show superior microwave dielectric properties, with an εr of 41.02, a Q×f value of 44,230 GHz (at 5.2 GHz), and τf value of +2.32 ppm/°C. 相似文献
11.
《Journal of the European Ceramic Society》2006,26(10-11):2117-2121
Li2O–Nb2O5–TiO2 based ceramic systems have been the candidate materials for LTCC application, due to their high dielectric constant and Q × f value and controllable temperature coefficient in the microwave region. However, the sintering temperature was relatively higher (above 1100 °C) for practical application. In this study, dielectric properties of Li(1+x−y)Nb(1−x−3y)Ti(x+4y)O3 solid solution were studied with different x and y contents and among them, the Li1.0Nb0.6Ti0.5O3 composition (x = 0.1, y = 0.1) was selected, due to its reasonable dielectric properties to determine the possibility of low temperature sintering. The effects of 0.17Li2O–0.83V2O5, as a sintering agent, on sinterability and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 ceramics were investigated as a function of the sintering agent content and sintering temperature. With addition of 0.17Li2O–0.83V2O5 above 0.5 wt%, the specimens were well densified at a relatively lower temperature of 850 °C. Only slight decrease in apparent density was observed with increasing 0.17Li2O–0.83V2O5 content above 0.75 wt%. In the case of 0.5 wt% 0.17Li2O–0.83V2O5 addition, the values of dielectric constant and Q × f reached maximum. Further addition caused inferior microstructure, resulting in degraded dielectric properties. For the specimens with 0.5 wt% 0.17Li2O–0.83V2O5 sintered at 850 °C, dielectric constant, Q × f and TCF values were 64.7, 5933 GHz and 9.4 ppm per °C, respectively. 相似文献
12.
《Ceramics International》2016,42(14):15855-15860
A novel low-fired microwave dielectric ceramic with composition of Ba4CuTi11O27 was prepared by a conventional solid-state reaction method. A single-phase Ba4CuTi11O27 ceramic could be well densified after sintering above 950 °C for 4 h in air. A refinement using X-ray powder diffraction data was carried out in the Rietveld method using the parameters of Ba4Ti12O27 as a starting model. Ba4CuTi11O27 ceramic sintered at 975 °C has a monoclinic structure (C12/m1) with lattice parameters of a=19.8061(4) Å, b=11.4456(2) Å, c=9.9131(2) Å, β=108.8988(15) Å, V=2126.08(8) Å3, Z=4. The Ba4CuTi11O27 ceramics exhibited a low sintering temperature (~975 °C) and good microwave dielectric properties with Q×f value of 15,040 GHz, εr of 36.3 and τf value 11.9 ppm/°C. More importantly, the Ba4CuTi11O27 dielectrics demonstrated good chemical compatibility with Ag when sintered at 950 °C, keeping excellent microwave dielectric properties with Q×f=12,130 GHz, εr=36.1, τf=12.1 ppm/°C, which indicates that Ba4CuTi11O27 ceramic is a candidate for LTCC devices. 相似文献
13.
《Journal of the European Ceramic Society》2007,27(8-9):3053-3057
The low sintering temperature and the good dielectric properties such as high dielectric constant (ɛr), high quality factor (Q × f) and small temperature coefficient of resonant frequency (τf) are required for the application of chip passive components in the wireless communication technologies. In the present study, the sintering behaviors and dielectric properties of Ba3Ti4Nb4O21 ceramics were investigated as a function of B2O3–CuO content. Ba3Ti4Nb4O21 ceramics with B2O3 or CuO addition could be sintered above 1100 °C. However, the additions of both B2O3 and CuO successfully reduced the sintering temperature of Ba3Ti4Nb4O21 ceramics from 1350 to 900 °C without detriment to the microwave dielectric properties. From the X-ray diffraction (XRD) studies, the sintering behaviors and the microwave dielectric properties of low-fired Ba3Ti4Nb4O21 ceramics were examined and discussed in the formation of the secondary phases. The Ba3Ti4Nb4O21 sample with 1 wt% B2O3 and 3 wt% CuO addition, sintered at 900 °C for 2 h, had the good dielectric properties: ɛr = 65, Q × f = 16,000 GHz and τf = 101 ppm/°C. 相似文献
14.
《Ceramics International》2017,43(2):1682-1687
Microwave dielectric properties of Li2Mg3−xCaxTiO6 (x=0–0.18) ceramics were studied using a conventional solid-state route to find temperature stable and high Q microwave ceramics. As the calcination temperature was 500 °C, the Li2TiO3 phase with monoclinic rock salt structure in C2/c space group started to form. When the samples were calcined from 600 °C to 900 °C, the XRD patterns exhibited a remarkable chemical reaction between the MgO and Li2TiO3 phases, which eventually formed the Li2Mg3TiO6 phase. The results indicated the Li2Mg3TiO6and CaTiO3 co-existed with each other and formed a stable composite system when the calcium content was added. The SEM photographs indicated that the pores caused by the Li evaporation could be effectively reduced due to the appearance of CaTiO3. As x was increased from 0 to 0.18, the relative density was significantly improved due to the elimination of pores. As the Ca content increased, the dielectric constant (εr) increased from 14.8 to 20.6; the quality factor (Q×f) decreased from 148,713 GHz to 79,845 GHz, and the temperature coefficient of resonant frequency (τf) significantly increased from −42.4 to +10.8 ppm/°C due to the increased amount of CaTiO3. Therefore, at x=0.12, the LMCxT ceramics sintered at 1280 °C for 6 h displayed excellent comprehensive properties of εr=17.8,Q×f=102,246 GHz and τf=−0.7 ppm/°C. 相似文献
15.
Pseudobrookite-type Mg5Nb4O15 ceramics were prepared by aqueous sol–gel process and microwave dielectric properties were investigated. Highly reactive nanosized Mg5Nb4O15 powders were successfully synthesized at 600 °C in oxygen atmosphere with particle sizes of 20–40 nm firstly and then phase evolution was detected by DTA-TG and XRD. Sintering characteristics and microwave dielectric properties of Mg5Nb4O15 ceramics were studied at different temperatures ranging from 1200 °C to 1400 °C. With the increase of sintering temperature, density, ?r and Q·f values increased, and then saturated at 1300 °C. Excellent microwave properties of ?r ~11.3, Q·f ~43,300 GHz and τf ~?58 ppm/°C, were obtained finally. The sintering temperature of Mg5Nb4O15 ceramics was significantly reduced by aqueous sol–gel process compared to conventional solid-state methods. 相似文献
16.
《Ceramics International》2016,42(13):14573-14580
BaO-Sm2O3-5TiO2 (BST5) ceramics with NdAlO3 additions of up to 15 wt% were produced with a solid state reaction method, and their structural and microwave dielectric properties were determined. Experimental results showed that NdAlO3 neither merged nor altered the orthorhombic tungsten bronze structure of the main phase of the produced ceramics (except for a shrinkage in the crystal lattice), but it was segregated in distinct grains in the microstructure of the produced ceramics. However, the amount of NdAlO3 strongly influenced the densification and the microstructure (i.e. grain shape and size) of the produced ceramics. Analysis of the experimental results suggests that the microstructural features can be correlated to the dielectric properties of these ceramics. Accordingly, the dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) of the produced BLT5 ceramics can be tuned with the amount of NdAlO3 additions and the sintering process parameters. The best dielectric properties were achieved for BaO-Sm2O3-5TiO2 ceramics with 7.5% NdAlO3 (εr=73.22, Q×f =10,300 GHz, and τf=−1.05 ppm/°C). 相似文献
17.
Li2(Mg0.94M0.06)Ti3O8 (M=Zn, Co, and Mn) ceramics were synthesized by the conventional solid-state reaction route. The effect of M (Zn, Co, and Mn) substitution on the structure, microstructure and microwave dielectric properties of Li2(Mg0.94M0.06)Ti3O8 has been investigated. The XRD patterns of sintered samples revealed the single-phase formation with spinel structure. With the increase in ionic radius of M, the Qf value decrease is attributed to the decrease of packing fraction and grain size. The Li2(Mg0.94Zn0.06)Ti3O8 ceramic sintered at 1075 °C for 4 h showed the best microwave dielectric properties with a dielectric constant of 27.1, a Qf value of 44 800 GHz, and a temperature coefficient of resonant frequency of (+)1.9 ppm/°C. 相似文献
18.
0.87(Mg0.7Zn0.3)TiO3–0.13(Ca0.61La0.26)TiO3 (referred to as 87MZCLT) ceramics were prepared by microwave sintering and conventional sintering. The experimental results demonstrated that the sintering cycle of 87MZCLT ceramics was greatly shortened and the impurity phase (Mg0.7Zn0.3)Ti2O5 was eliminated by microwave sintering. Moreover, the 87MZCLT ceramics prepared by microwave sintering show more uniform, fine-grained microstructure as well as much less Zn evaporation. As a result, the quality factor was increased by 40% compared with conventional sintering. All samples were sintered at 1275 °C for 20 min with heating and cooling rate of 15 °C/min and gave excellent microwave dielectric properties: ?r = 26.21, Q × f = 120,000 GHz, τf = ?3 ppm/°C. 相似文献
19.
《Journal of the European Ceramic Society》2007,27(1):261-265
The effect of B2O3 addition on the sintering, microstructure and the microwave dielectric properties of LiNb0.6Ti0.5O3 ceramics have been investigated. It is found that low-level doping of B2O3 (≤2 wt.%) can significantly improve the densification and dielectric properties of LiNb0.6Ti0.5O3 ceramics. Due to the liquid phase effect of B2O3 addition, LiNb0.6Ti0.5O3 ceramics could be sintered to a theoretical density higher than 95% even at 880 °C. No secondary phase was observed for the B2O3-doped ceramics. There is no obvious degradation in dielectric properties for the ceramics with B2O3 additions. In the case of 1 wt.% B2O3 addition, the ceramics sintered at 880 °C show good microwave dielectric properties of ɛr = 70, Q × f = 5400 GHz, τf = −6.39 ppm/°C. It represents that the ceramics could be promising for multilayer low-temperature co-fired ceramics (LTCC) applications. 相似文献
20.
《Ceramics International》2017,43(5):4570-4575
Novel monoclinic Bi2O3-xRE2O3-yMoO3 (RE=Pr, Nd, Sm, and Yb) based low temperature co-fired ceramics (LTCC) systems with high sintering density and low microwave dielectric loss are synthesized by conventional solid state reaction technique. The structure and dielectric properties of Bi2O3-xRE2O3-yMoO3 ceramics are investigated. Dense BiNdMoO6 ceramics sintered at 900 °C for 8 h in air have a low dielectric constant εr=~7.5, a high quality factor Q×f=~ 24, 800 GHz at 7.0 GHz, and τf=~−16 ppm/̊C. Especially, good chemical compatibility of BiNdMoO6 with Ag electrodes is represented as well. In contrast, BiSmMoO6 ceramics sintered at 1000 °C for 8 h show enhanced Q×f=~43, 700 GHz at 7.8 GHz with εr=~8.5 and τf=~−27 ppm/°C. Bi2O3-xRE2O3-yMoO3 (RE=Pr, Nd, Sm, and Yb) based ceramics could be considered as promising microwave ceramics for LTCC applications. 相似文献