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1.
The influences of B2O3 and CuO (BCu, B2O3: CuO = 1:1) additions on the sintering behavior and microwave dielectric properties of LiNb0.6Ti0.5O3 (LNT) ceramics were investigated. LNT ceramics were prepared with conventional solid-state method and sintered at temperatures about 1,100 °C. The sintering temperature of LNT ceramics with BCu addition could be effectively reduced to 900 °C due to the liquid phase effects resulting from the additives. The addition of BCu does not induce much degradation in the microwave dielectric properties. Typically, the excellent microwave dielectric properties of εr = 66, Q × f = 6,210 GHz, and τ f  = 25 ppm/oC were obtained for the 2 wt% BCu-doped sample sintered at 900 °C. Chemical compatibility of silver electrodes and low-fired samples has also been investigated.  相似文献   

2.
Gd3+ was chosen as a substitute for Bi3+ in BiNbO4 ceramics, and the substitution effects on the sintering performance and microwave dielectric properties were studied in this paper. The high temperature triclinic phase was observed only in the Bi0.98Gd0.02NbO4 ceramics when sintered at 920 °C. Both bulk densities and dielectric constant (εr) increased with the sintering temperature, while decreased with the Gd content. The quality factor (Q) exhibited a correlation to the Gd content and the microstructures of Bi1−x Gd x NbO4 ceramics. At the sintering temperature of 900 °C, Bi0.992Gd0.008NbO4 ceramics exhibited microwave dielectric properties of εr ∼ 43.87, Q × f ∼ 16,852 GHz (at 4.3 GHz), and its temperature coefficient of resonant frequency (τf) was found to be near-to-zero.  相似文献   

3.
Magnesium titanate was synthesized by the solid state reaction. Powder XRD method was used to identify the phases and content, which indicates that pure phase of MgTiO3 can be synthesized by the solid state reaction even without the addition of excess MgO. Doped with 5 at.% CaTiO3 and 6 wt.% ZnNb2O6, MgTiO3 ceramics sintered at 1300 °C possess excellent microwave dielectric properties: a dielectric constant εr of 21, a τ f value of 0 ppm/°Cand a Q × f value of 130,000 GHz (at 13 GHz).  相似文献   

4.
Ba5Nb4O15 powders were synthesized by molten-salt method in NaCl–KCl flux at a low temperature of 650–900 °C for 2 h, which is lower than that of the conventional solid-state reaction. This simple process involved mixing of the raw materials and salts in a certain proportion. Subsequent calcination of the mixtures led to Ba5Nb4O15 powders at 650–900 °C. XRD and SEM techniques were used to characterize the phase and morphology of the fabricated Ba5Nb4O15 powders, respectively. After sintering at 1,300 °C for 2 h, the densified Ba5Nb4O15 ceramics with good microwave dielectric properties of εr = 39.2, Q × f approximated as 27,200 GHz and τ f  = 72 ppm/°C have been obtained.  相似文献   

5.
The effects of co-doped CuO and B2O3 addition on the sintering temperature, microstructure and microwave dielectric properties of MgNb2O6 ceramics prepared with conventional solid-state route were investigated. When both CuO and B2O3 were added, the MgNb2O6 ceramics were not only sintered at 1000 °C but also improved the Qf value. MgNb2O6 ceramics can be well sintered to approach to 98.1% theoretical density with 2.0 wt.% CuO–B2O3 additive due to its liquid phase effect. With 2.0 wt.% CuO–B2O3, a dielectric constant of 21.5, a Qf value of 108,000(GHz) and a τ f value of −44 ppm/°C of MgNb2O6 ceramics doped with CuO–B2O3 sintered at 1050 °C for 2 h are obtained. The variation of ε r, Qf and τ f were also explained based on the difference in microstructures.  相似文献   

6.
《Materials Letters》2006,60(9-10):1188-1191
The effects of Bi2O3–V2O5 additive on the microstructures, the phase formation and the microwave dielectric properties of MgTiO3 Ceramics were investigated. The Bi2O3–V2O5 addition lowered the sintering temperature of MgTiO3 ceramics effectively from 1400 to 875 °C due to the liquid-phase effect. The microwave dielectric properties were found to strongly correlate with the amount of Bi2O3–V2O5 addition. The saturated dielectric constant decreased and the maximum Qf values increased with the increasing V2O5 content, which is attributed to the variation of the second phase including Bi2Ti2O7, Bi4V1.5Ti0.5O10.85 and BiVO4. At 875 °C, MgTiO3 ceramics with 5.0 mol% Bi2O3–7 mol% V2O5 gave excellent microwave dielectric properties: εr = 20.6,Qf = 10420 GHz (6.3 GHz).  相似文献   

7.
The effects of B2O3–CuO (BCu, the weight ratio of B2O3 to CuO is 1:1) addition on the sintering behavior, microstructure, and the microwave dielectric properties of 3Li2O–Nb2O5–3TiO2 (LNT) ceramics have been investigated. The low-amount addition of BCu can effectively lower the sintering temperature of LNT ceramics from 1125 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 2 wt% BCu-added ceramic sintered at 900 °C has better microwave dielectric properties of ε r  = 50.1, Q × f = 8300 GHz, τ f  = 35 ppm/°C. Silver powders were cofired with the dielectric under air atmosphere at 900 °C. The SEM and EDS analysis showed no reaction between the dielectric ceramic and silver powders. This result shows that the LNT dielectric materials are good candidates for LTCC applications with silver electrode.  相似文献   

8.
Phase purity, microstructure, sinterability and microwave dielectric properties of BaCu(B2O5)-added Li2ZnTi3O8 ceramics and their cofireability with Ag electrode were investigated. A small amount of BaCu (B2O5) can effectively reduce the sintering temperature from 1075°C to 925°C, and it does not induce much degradation of the microwave dielectric properties. Microwave dielectric properties of ε r = 23·1, Q × f = 22,732 GHz and τ f = − 17·6 ppm/°C were obtained for Li2ZnTi3O8 ceramic with 1·5 wt% BaCu(B2O5) sintered at 925°C for 4 h. The Li2ZnTi3O8 +BCB ceramics can be compatible with Ag electrode, which makes it a promising microwave dielectric material for low-temperature co-fired ceramic technology application.  相似文献   

9.
The effect of CuO and B2O3 co-doping on the sintering behavior, microstructure and microwave dielectric properties of tungsten bronze type Ba4Nd9.3Ti18O54 (BNT) ceramics has been investigated by means of a traditional solid-state mixed oxide route. On the one hand, it was indicated that the mixture of CuO and B2O3 is an effective sintering aid for BNT matrix compositions owing to the existence of a low-temperature eutectic reaction. On the other hand, it was found that the addition of CuO and B2O3 has an obvious effect on microwave dielectric properties of BNT ceramics, depending on the amount of sintering aids, the sample density and microstructure. The liquid phases from sintering aids can promote densification, but simultaneously induce grain growth which tends to decrease the sintering driving force. BNT ceramics doped with 3 wt% CuO–B2O3 mixture can be well sintered at 950°C for 4 h and still exhibit relatively good microwave dielectric properties.  相似文献   

10.
Temperature stable high-K LTCC material was prepared. The influence of fabrication process on the crystalline phases, microstructures and microwave dielectric properties of TiO2-Bi2O3-CuO ceramics were investigated. The crystalline phases and microstructures of TiO2-Bi2O3-CuO ceramics were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. It was found that rutile TiO2 phase and Bi2Ti4O11 phase co-existed in the TiO2-Bi2O3-CuO ceramics. Separate TiO2 grains and Bi2Ti4O11 grains distributed uniformly in the ceramic matrix. The composition 0.92TiO2-0.08Bi2Ti4O11 with 2 wt% CuO addition that was sintered at 900 °C for 2 h showed high dielectric constant (εr ~ 81), high quality factor (Q × f ~ 3,500 GHz) and near zero temperature coefficient of resonant frequency (τf ~ −5.1 ppm/°C), meanwhile the compatibility test showed that it could co-fire with silver electrode. The processing-microstructure-property interrelationship was also studied.  相似文献   

11.
Low temperature sintering and dielectric properties of Ba2Ti3Nb4O18 ceramics with ZnO–B2O3–SiO2 (ZBS) frit and lithium salts addition were investigated for silver co-sintering application. The sintering temperature of dense Ba2Ti3Nb4O18 ceramics with ZBS frit or LiNO3 addition was effectively lowered to 950 or 1,000 °C, respectively. LiNO3 is found to be more efficient than LiF or Li2CO3 to lower the sintering temperature of Ba2Ti3Nb4O18 ceramics. The sintering temperature of 900 °C was obtained for the Ba2Ti3Nb4O18 ceramics with a combination of ZBS frit and LiNO3 addition. The dielectric properties of Ba2Ti3Nb4O18 ceramics with 1 wt.% ZBS and 0.5 wt.% LiNO3 sintered at 900 °C are as follows: εr ~ 37.8, tan δ ~ 0.0003, τε ~ 4.6 ppm/°C.  相似文献   

12.
Ca4-xMgxLa2Ti5O17 ceramics were prepared by a solid state ceramic route for x = 0, 0.5, 1, 2, 3 and 4. The structure and microstructure of the ceramics were investigated using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction results show that the Ca4-x Mg x La2Ti5O17 adopts an orthorhombic crystal structure with no secondary phase observed for x from 0 to 0.5. Secondary phase, MgTiO3 occurs with further increasing doping level (1 ≤ x ≤ 3). When x = 4, mixture phases La0.66TiO2.993, MgTiO3 and a trace of unknown phase coexist. Ca4La2Ti5O17 ceramic exhibits a relative permittivity (εr) ~ 65, quality factor (Q × f) ~13,338 GHz (at ~4.75 GHz), and temperature coefficient of resonant frequency (τ f ) ~ 165 ppm/°C. The sintering temperature was distinctly reduced from 1,580 °C for x = 0 to 1,350 °C for x = 4. With increasing Mg content, εr and τf obviously decrease, while Q × f value initially decreases and then increases. The ceramic for x = 2 shows εr ~ 50, Q × f ~ 9,451 and τ f  ~ 62.5 ppm/°C. By the complete replacement of Ca with Mg, Mg4La2Ti5O17 ceramic sintered at 1,350 °C for 4 h combines a high dielectric permittivity (ε r  = 31), high quality factor (Q × f ~ 15,021) and near-zero temperature coefficient of resonant frequency (τ f  ~ 4.0 ppm/°C). The materials are suitable for microwave applications.  相似文献   

13.
The microwave dielectric properties and the microstructures of Sm(Co1/2Ti1/2)O3 ceramics with B2O3 additions (0.25 and 0.5 wt%) prepared by conventional solid-state route have been investigated. The prepared Sm(Co1/2Ti1/2)O3 exhibited a mixture of Co and Ti showing 1:1 order in the B-site. Doping with B2O3 (up to 0.5 wt%) can effectively promote the densification of Sm(Co1/2Ti1/2)O3 ceramics with low sintering temperature. It is found that Sm(Co1/2Ti1/2)O3 ceramics can be sintered at 1,260 °C due to the grain boundary phase effect of B2O3 addition. At 1,290 °C, Sm(Co1/2Ti1/2)O3 ceramics with 0.5 wt% B2O3 addition possess a dielectric constant (ε r) of 27.7, a Q × f value of 33,600 (at 9 GHz) and a temperature coefficient of resonant frequency (τf) of −11.4 ppm/ °C. The B2O3-doped Sm(Co1/2Ti1/2)O3 ceramics can find applications in microwave devices requiring low sintering temperature.  相似文献   

14.
The microstructure, electrical properties, and DC-accelerated aging behavior of the ZnO-V2O5-Mn3O4 ceramics were investigated at different sintering temperatures of 850–925°C. The microstructure of the ZnO-V2O5-Mn3O4 ceramics consisted of ZnO grain as a primary phase, and Zn3(VO4)2 which acts as a liquid-phase sintering aid, in addition to Mn-rich phase as secondary phases. The maximum value (3,172 V/cm) and minimum value (977 V/cm) of breakdown field were obtained at sintering temperature of 850 and 900°C, respectively. The nonlinear coefficient exhibited the highest value, reaching 30 at 925°C and the lowest value, reaching 4 at 850°C. The optimum sintering temperature was 900°C, which exhibited not only high nonlinearity with 24 in nonlinear coefficient, but also the high stability, with %ΔE1mA = −0.9% and %∆α = −12.5% for DC-accelerated aging stress of 0.85 E1mA/85°C/24 h.  相似文献   

15.
The phase formation, sintering behavior and microwave dielectric properties of Bi2O3 and MnO2 co-doped [(Pb, Ca) La](Fe, Nb)O3+δ (PCLFN) ceramics were investigated. The Bi2O3 and MnO2 binary dopants formed stable and low melting temperature solubilities at grain boundary which resulted in an effectively lowered sintering temperature by about 140 °C a more rapid sintering process and enhanced bulk densities. Sintering procedure has significant effect on grain size and porosities in ceramics. With high sintering temperature and time, the evaporation of PbO scaled up from surface toward the bulk and resulted in a Pb2+ deficient layer up to 0.25 mm depth under ceramic surface. Investigation of sintering dynamic revealed that either volume diffusion or second-order interface mechanism controlled the grain growth in present system. An optimal microwave dielectric properties of εr = 91.1, Q f = 4,870 GHz and τ f = 18.5 ppm/°C could be obtained in Bi2O3 and MnO2 co-doped [(Pb, Ca) La](Fe, Nb)O3+δ ceramics sintered at 1,050 °C for 4 h when the quality ratio of Bi2O3/MnO2 was 1 and the doping content w = 1 wt%.  相似文献   

16.
CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2·45 GHz, 1·1 kW. The optimum calcination temperature using microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were sintered to 94% density at 1000°C/60 min. The microstructural studies carried out on these ceramics revealed the grain size to be in the range 1–7 μm. The dielectric constants for the microwave sintered (1000°C/60 min) ceramics were found to vary from 11000–7700 in the 100 Hz–00 kHz frequency range. Interestingly the dielectric loss had lower values than those sintered by conventional sintering routes and decreases with increase in frequency.  相似文献   

17.
A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li2TiO3 and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave dielectric properties of a relatively high permittivity (∼51), high × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li2O–0.17V2O5 (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties of εr = 51.3, × f = 7235 GHz, τ f  = 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices.  相似文献   

18.
Effects of Li2O–B2O3 on the sintering behavior and the microwave dielectric properties of (Zn0.8Mg0.2)2SiO4–TiO2 ceramics were investigated as a function of Li2O–B2O3 content and sintering temperature. The Li2O–B2O3 combined additives successfully reduced the sintering temperature of (Zn0.8Mg0.2)2SiO4–TiO2 ceramics from 1,250 °C to 900 °C. With the increase of Li2O–B2O3 content, the TiO2 phase decreased and the unknown second phase increased, which led to the dielectric constant (ε r ) and the maximum Q × f value decrease, and the temperature coefficient of resonant frequency (τ f ) shift to a negative value. The specimens with 3 wt%Li2O–B2O3 sintered at 900 °C for 2 h showed ε r of 8.84, Q × f value of 15,500 GHz, and τ f of 17.8 ppm/°C. And the material was compatible with Ag electrodes, which made it a promising ceramic for low temperature co-fired ceramics technology application.  相似文献   

19.
The effects of replacement of MgO by CaO on the sintering and crystallization behavior of MgO–Al2O3–SiO2 system glass-ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature firstly increased and then decreased, the melting temperature was lowered and the crystallization temperature of the glass-ceramics shifted clearly towards higher temperatures. With the replacement of MgO by less than 3 wt.% CaO, the predominant crystalline phase in the glass-ceramics fired at 900 °C was found to be α-cordierite and the secondary crystalline phase to be μ-cordierite. When the replacement was increased to 10 wt.%, the predominant crystalline phase was found to be anorthite and the secondary phase to be α-cordierite. Both thermal expansion coefficient (TCE) and dielectric constant of samples increases with the replacement of MgO by CaO. The dielectric loss of sample with 5 wt.% CaO fired at 900 °C has the lowest value of 0.08%. Only the sample containing 5 wt.% and10 wt.% CaO (abbreviated as sample C5 and C10) can be fully sintered before 900 °C. Therefore, a dense and low dielectric loss glass-ceramic with predominant crystal phase of α-cordierite and some amount of anorthite was achieved by using fine glass powders (D50 = 3 μm) fired at 875–900 °C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample C5 firstly increases and then decreases with sintering temperature, which closely corresponds to its relative density. The TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures depends on not only its relative density but also its crystalline phases. The dense and crystallized glass-ceramic C5 exhibits a low sintering temperature (≤900 °C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10−3) at 1 MHz, a low TCE (4.0–4.25 × 10−6 K−1), very close to that of Si (∼3.5 × 10−6 K−1), and a higher flexural strength (≥134 MPa), suggesting that it would be a promising material in the electronic packaging field.  相似文献   

20.
The Zn2SiO4 ceramics with the addition of BaO and B2O3 are fabricated by traditional solid-state preparation process at a sintering temperature of 900 °C. The introduction of BaO and B2O3 to the binary system ZnO-SiO2 is achieved by adding 10 and 20 wt. % flux BB to the mixed ZnO-SiO2 ceramic powders pre-sintered at 1,100 °C, respectively. The chemical composition of the flux BB (50 wt.%BaO-50 wt.% B2O3) is located at a liquid phase zone with a temperature range of about 869–900 °C in the binary diagram BaO-B2O3. In addition, the introduction of BaO and B2O3 to the binary system ZnO-SiO2 is also achieved by the means of a chemical combination of H2SiO3, H3BO3, ZnO and Ba(OH)2·8H2O, which can result in the formation of the hydrated barium borates with low melting characteristics. In turn, by the liquid sintering aid of the barium borate melts, the preparation process of the Zn2SiO4 ceramics can be further simplified. In the two preparation methods, the Zn2SiO4 ceramics with the 1.5–2.0 ZnO/SiO2 molar ratios and the addition of a 10 wt. % flux BB can show good dielectric properties whereas the bending strength mainly depends on the microstructure of the Zn2SiO4 ceramics and SiO2 content in the composition of the specimen.  相似文献   

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