共查询到20条相似文献,搜索用时 31 毫秒
1.
Jigui Cheng Qiumei Jiang Haigen He Junfang Yang Yifang Wang Jianfeng Gao 《Materials Chemistry and Physics》2011
Y2O3–Sm2O3 co-doped ceria (YSDC) powder was synthesized by a gel-casting method using Ce(NO3)3·6H2O, Sm2O3 and Y2O3 as raw materials. Phase structure of the synthesized powders was characterized by X-Ray diffraction analysis. Sinterability of the powders was investigated by testing the relative density and observing the microstructure of the sintered YSDC samples. Electrical conductivity of the sintered YSDC samples was measured using impedance spectra method. Single solid oxide fuel cells based on the YSDC electrolyte were also assembled and tested. The results showed that YSDC powders with single-phase fluorite structure can be obtained by calcining the dried gelcasts at temperature above 800 °C. Average particle size of the YSDC powder is 50–100 nm. Relative density of more than 95% of the theoretical can be achieved by sintering the YSDC compacts at temperature above 1400 °C. The sintered YSDC sample has an ionic conductivity of 4.74 × 10−2 S cm−1 at 800 °C in air. Single fuel cells based on the YSDC electrolyte with 50 μm in thickness were tested using humidified hydrogen as fuel and air as oxidant, and maximum power densities of about 190 and 112 mW cm−2 were achieved at 700 and 600 °C, respectively. 相似文献
2.
Ba4MgTi11O27 microwave dielectric ceramic was investigated using X-ray diffraction, scanning electron microscopy and dielectric measurement. The pure Ba4MgTi11O27 ceramic shows a high sintering temperature (∼1275 °C) and good microwave dielectric properties as Q × f of 19,630 GHz, ?r of 36.1, τf of 14.6 ppm/°C. It was found that the addition of BaCu(B2O5) (BCB) can effectively lower the sintering temperature from 1275 to 925 °C, and does not induce much degradation of the microwave dielectric properties. The BCB-doped Ba4MgTi11O27 ceramics can be compatible with Ag electrode, which makes it a promising ceramic for LTCC technology application. 相似文献
3.
M.V. Nikoli? K.M. Paraskevopoulos T.T. Zorba V.D. Blagojevi? P.M. Nikoli? 《Materials Research Bulletin》2007,42(8):1492-1498
Single phase complex spinel (Mn, Ni, Co, Fe)3O4 samples were sintered at 1050, 1200 and 1300 °C for 30 min and at 1200 °C for 120 min. Morphological changes of the obtained samples with the sintering temperature and time were analyzed by X-ray diffraction and scanning electron microscope (SEM). Room temperature far infrared reflectivity spectra for all samples were measured in the frequency range between 50 and 1200 cm−1. The obtained spectra for all samples showed the presence of the same oscillators, but their intensities increased with the sintering temperature and time in correlation with the increase in sample density and microstructure changes during sintering. The measured spectra were numerically analyzed using the Kramers-Krönig method and the four-parameter model of coupled oscillators. Optical modes were calculated for six observed ionic oscillators belonging to the spinel structure of (Mn, Ni, Co, Fe)3O4 of which four were strong and two were weak. 相似文献
4.
Yanzhong Wang Anthony ChesnaudEmile Bevillon Jinlong YangGuilhem Dezanneau 《Materials Science and Engineering: B》2011,176(15):1178-1183
The effects of ZnO additive on the phase formation, microstructure and electrical conduction of Y-doped BaSnO3 have been investigated. The single-phase and dense BaSn0.75Y0.25O3−δ compound with 4 mol% ZnO additive was successfully prepared after sintering at 1300 °C, which significantly reduces the sintering temperature. The conductivities measured under dry and wet air atmospheres reveal that the bulk conductivity of BaSn0.71Y0.25Zn0.04O3−δ is much lower than that of BaSn0.75Y0.25O3−δ. However, ZnO as a sintering aid does not affect the bulk conductivity. The total conductivity of BaSn0.75Y0.25O3−δ with ZnO as the sintering aid is slightly higher than that of unmodified BaSn0.75Y0.25O3−δ, and reaches 2.4 × 10−3 S cm−1 at 621 °C. Therefore, this material can be used as a proton-conducting electrolyte for intermediate temperature solid oxide fuel cells. 相似文献
5.
The effect of CaO-SiO2-B2O3 (CSB) glass addition on the sintering temperature and dielectric properties of BaxSmyTi7O20 ceramics has been investigated using X-ray diffraction, scanning electron microscopy and differential thermal analysis. The CSB glass starts to melt at about 970 °C, and a small amount of CSB glass addition to BaxSmyTi7O20 ceramics can greatly decrease the sintering temperature from about 1350 to about 1260 °C, which is attributed to the formation of liquid phase. It is found that the dielectric properties of BaxSmyTi7O20 ceramics are dependent on the amount of CSB glass and the microstructures of sintered samples. The product with 5 wt% CSB glass sintered at 1260 °C is optimal in these samples based on the microstructure and the properties of sintering product, when the major phases of this material are BaSm2Ti4O12 and BaTi4O9. The material possesses excellent dielectric properties: ?r = 61, tan δ = 1.5 × 10−4 at 10 GHz, temperature coefficient of dielectric constant is −75 × 10−6 °C−1. 相似文献
6.
Yi-Cheng Liou Chi-Ting Wu Ko-Hao Tseng Tzu-Chin Chung 《Materials Research Bulletin》2005,40(9):1483-1489
Synthesis of BaTi4O9 ceramics by a reaction-sintering process was investigated. The mixture of raw materials for stoichiometric BaTi4O9 were pressed and sintered into ceramics without any calcination stage involved. Pure BaTi4O9 phases were obtained at 1150-1280 °C. High-sintered density, 98.2-99.5% of theoretical value (4.533 g/cm3), can be obtained for pellets sintered at 1200-1280 °C for 2-6 h. Some rod-shaped grains 3-7 μm in the longitudinal axis appear in pellets sintered at 1230 °C. Both the size and the amount of these rod-shaped grains increase at higher sintering temperature. 相似文献
7.
The influences of P2O5 doping on the sintering behavior, phase formation and properties of barium zirconate ceramics were investigated. Unmodified BaZrO3 was difficult to densify, even at 1600 °C. Only a porous microstructure could be obtained. However, doping BaZrO3 with P2O5 markedly enhances its sinterability. 94.2% of theoretical density was achieved with the inclusion of 4 mol% P2O5 sintered at 1600 °C for 4 h. The bending strength of the samples sintered at 1600 °C for 4 h was improved by almost 8 times by the addition of 4 mol% P2O5. The average bending strength of 152.3 ± 16.7 MPa was obtained. The Vickers hardness of 4 mol% P2O5 modified BaZrO3 reaches 8.8 ± 0.4 GPa. 相似文献
8.
The phases, microstructure and microwave dielectric properties of ZnTiNb2O8 ceramics with BaCu(B2O5) additions prepared by solid-state reaction method have been investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The pure ZnTiNb2O8 ceramic shows a high sintering temperature of about 1250 °C. However, it was found that the addition of BaCu(B2O5) lowered the sintering temperature of ZnTiNb2O8 ceramics from above 1250 °C to 950 °C due to the BCB liquid-phase. The results showed that the microwave dielectric properties were strongly dependent on densification, crystalline phases and grain size. Addition of 3 wt% BCB in ZnTiNb2O8 ceramics sintered at 950 °C afforded excellent dielectric properties of ?r = 32.56, Q × f = 20,100 GHz (f = 5.128 GHz) and τf = −64.87 ppm/°C. These represent very promising candidates for LTCC dielectric materials. 相似文献
9.
E.L. Papadopoulou Z.A. Viskadourakis A.V. Pennos E. Aperathitis 《Thin solid films》2008,516(7):1449-1452
SrCu2O2 (SCO) thin films have been fabricated by pulsed laser deposition at oxygen partial pressures between 5 × 10− 5-5 × 10− 2 mbar and substrate temperatures from 300 °C to 500 °C. All films were single-phase SrCu2O2, p-type materials. Films deposited at a substrate temperature of 300 °C and oxygen pressure 5 × 10− 4 mbar exhibited the highest transparency (∼ 80%), having conductivity 10− 3 S/cm and carrier concentration around 1013 cm− 3. Films deposited at oxygen partial pressure higher than 10− 3 mbar exhibited higher conductivity and carrier concentration but lower transmittance. Depositions at substrate temperatures higher than 300 °C gave films of high crystallinity and transmittance even for films as thick as 800 nm. The energy gap of SrCu2O2 thin films was found to be around 3.3 eV. 相似文献
10.
Low temperature co-fired ceramic (LTCC) is prepared by sintering a glass selected from CaO-SiO2-B2O3 system, and its sintered bodies are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the optimal sintering temperature for this glass-ceramic is 820 °C for 15 min, and the major phases of this material are CaSiO3, CaB2O4 and SiO2. The glass-ceramic possesses excellent dielectric properties: ?r = 6.5, tan δ < 2 × 10−3 at 10 MHz, temperature coefficient of dielectric constant about −51 × 10−6 °C−1 and coefficient of thermal expansion about 8 × 10−6 °C−1 at 20-400 °C. Thus, this material is supposed to be suitable for the tape casting process and be compatible with Ag electrode, which could be used as the LTCC materials for the application in wireless communications. 相似文献
11.
n-type SbI3-doped 95%Bi2Te3+5%Bi2Se3 compounds were prepared by a rapid solidification and extrusion at the temperature range 420-480 °C using an extrusion ratio of 25:1. The microstructure and thermoelectric properties of the compounds were investigated as a function of extrusion temperature. The fabricated powder consists of homogeneous Bi2Te3+Bi2Se3 solid solution and the relative density of over 99% was obtained by hot extrusion. The values of Seebeck coefficient for the compounds hot extruded at 420, 450, and 480 °C were −160.8, −170.2, and −165.7 μV K−1, respectively. The values of electrical resistivity (ρ) for the compounds hot extruded at 420, 450, and 480 °C were 0.49, 0.57, and 0.51×10−5 Ω m, respectively. The maximum power factor value of the compounds hot extruded at 480 °C was 53.8×106 μW cm−1 K−2. 相似文献
12.
The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and microwave dielectric properties of the 11Li2O-3Nb2O5-12TiO2 (LNT) ceramics have been investigated. With the low-level doping of B2O3 (≤2 wt.%), the sintering temperature of the LNT ceramic could be effectively reduced to 900 °C. The B2O3-doped LNT ceramics are also composed of Li2TiO3ss and “M-phase” phases. No other phase could be observed in the 0.5-2 wt.% B2O3-doped ceramics sintered at 840-920 °C. The addition of B2O3 induced no obvious degradation in the microwave dielectric properties but increased the τf values. Typically, the 0.5 wt.% B2O3-doped ceramics sintered at 900 °C have better microwave dielectric properties of ?r = 49.2, Q × f = 8839 GHz, τf = 57.6 ppm/°C, which suggest that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures. 相似文献
13.
Reactive hot-press (1800-1880 °C, 30 MPa, vacuum) is used to fabricate relatively dense B4C matrix light composites with the sintering additive of (Al2O3 +Y2O3). Phase composition, microstructure and mechanical properties are determined by methods of XRD, SEM and SENB, etc. These results show that reactions among original powders B4C, Si3N4 and TiC occur during sintering and new phases as SiC, TiB2 and BN are produced. The sandwich SiC and claviform TiB2 play an important role in improving the properties. The composites are ultimately and compactly sintered owing to higher temperature, fine grains and liquid phase sintering, with the highest relative density of 95.6%. The composite sintered at 1880 °C possesses the best general properties with bending strength of 540 MPa and fracture toughness of 5.6 MPa m1/2, 29 and 80% higher than that of monolithic B4C, respectively. The fracture mode is the combination of transgranular fracture and intergranular fracture. The toughening mechanism is certified to consist of crack deflection, crack bridging and pulling-out effects of the grains. 相似文献
14.
Stoichiometric lead magnesium niobate, Pb(Mg1/3Nb2/3)O3 (PMN), perovskite ceramics produced by reaction-sintering process were investigated. Without calcination, a mixture of PbO, Nb2O5, and Mg(NO3)2 was pressed and sintered directly. Stoichiometric PMN ceramics of 100% perovskite phase were obtained for 1, 2, and 4 h sintering at 1250 and 1270 °C. PMN ceramics with density 8.09 g/cm3 (99.5% of theoretical density 8.13 g/cm3) and Kmax 19,900 under 1 kHz were obtained. 相似文献
15.
Hao Yang Xianpeng Qin Jian Zhang Jan Ma Dingyuan TangShiwei Wang Qitu Zhang 《Optical Materials》2012,34(6):940-943
Nd:YAG transparent ceramics were fabricated by a reactive sintering method under vacuum using SiO2, MgO and compound additives (SiO2 and MgO) as sintering aids. The effects of SiO2 and MgO on the microstructure and sintering process of Nd:YAG ceramics were studied. High quality Nd:YAG ceramics with compound sintering aids obtained by vacuum sintering at 1780 °C are composed of grains of the size ∼10 μm, and their transmittance is 82% at 400 nm. It was found the absorption coefficient of 1.0 mol% Nd:YAG ceramic was 8.6 cm−1 at 808 nm and its absorption cross section was calculated to be 6.26 × 10−20 cm2. 相似文献
16.
The tetragonal gillespite type SrCuSi4O10 (SCS) was prepared by the conventional solid-state ceramic route. The SCS sintered at 1100 °C/6 h showed εr = 4.0 and tan δ = 1.1 × 10−3 at 5 GHz. The SCS has poor sinterability and the addition of lithium magnesium zinc borosilicate glass (20: Li2O, 20: MgO, 20: ZnO, 20: B2O3, 20: SiO2) lowered the sintering temperature and improved densification. The SCS ceramic with 5 wt.% LMZBS glass sintered at 900 °C has εr = 5.0 and tan δ = 1.9 × 10−3 at 5 GHz. The composite is chemically compatible with the common electrode material silver. 相似文献
17.
The effects of CuO-V2O5 addition on the sintering temperature and microwave dielectric properties of ZnO-Nb2O5-TiO2-SnO2 were investigated. The CuO-V2O5 addition lowered the sintering temperature of ZnO-Nb2O5-TiO2-SnO2 ceramics effectively from 1150 to 860 °C due to the liquid-phase effect of Cu2V2O7 and Cu3(VO4)2, as observed by XRD. The microwave dielectric properties were found to strongly correlate with the sintering temperature and the amount of CuO-V2O5 addition. The maximum Qf values decreased with increasing CuO-V2O5 content, due to the formation of the second phase, Cu3(VO4)2 and CuNbO3. Zero τf value can be obtained by properly adjusting the sintering temperature. At 860 °C, ZnO-Nb2O5-TiO2-SnO2 ceramics with 1.5 wt.% CuO-V2O5 gave excellent microwave dielectric properties: ?r = 42.3, Qf = 9000 GHz and τf = 8 ppm/°C. 相似文献
18.
In this study, we tried to lower the sintering temperature of Ba0.6Sr0.4TiO3 (BST) ceramics by several kinds of adding methods of Bi2O3, CuO and CuBi2O4 additives. The effects of different adding methods on the microstructures and the dielectric properties of BST ceramics have been studied. In the all additive systems, the single addition of CuBi2O4 was the most effective way for lowering the sintering temperature of BST. When CuBi2O4 of 0.6 mol% was mixed with starting BST powders and sintered at 1100 °C, the derived ceramics demonstrated dense microstructure with a low dielectric constant (? = 4240), low dielectric loss (tan δ = 0.0058), high tunability (Tun = 38.3%) and high Q value (Q = 251). It was noteworthy that the sintering temperature was significantly lowered by 350 °C compared with no-additive system, and the derived ceramics maintained the excellent microwave dielectric properties corresponding to pure BST. 相似文献
19.
Low temperature sintering of Pb(Zr,Ti)O3-Pb(Fe2/3W1/3)O3-Pb(Mn1/3Nb2/3)O3 (PZT-PFW-PMN) quaternary piezoelectric ceramics were studied with the use of YMnO3 as sintering aid. The sintering aid improved the sinterability of PZT-PFW-PMN ceramics due to the effect of YMnO3 liquid phase. The effects of YMnO3 contents and sintering temperature on the phase structure, density, dielectric and piezoelectric properties were investigated. The results show that the sintering temperature can be decreased and the electrical properties can be maintained by the YMnO3 addition. The optimized properties were obtained by doping 0.30 wt.% YMnO3 and sintering at 1020 °C, which are listed as follows: d33 = 341 pC/N, Kp = 0.57, Qm = 1393, tan δ = 0.0053, Tc = 304 °C, Pr = 17.13 μC/cm2 and Ec = 11.15 kV/cm, which make this system be a promising material for multilayer piezoelectric actuator and transformer applications. 相似文献
20.
To obtain TCO films for wavelengths shorter than the visible range, Ga2O3 was added to the In2O3-ZnO system as an impurity. Using pulsed laser deposition (PLD), two kinds of targets, InGaZnO4 and InGaZn3O6, were deposited. Although the In-Ga-Zn-O films obtained deviated from the stoichiometry of InGaZnO4, they were amorphous at a substrate temperature below 250 °C. We obtained the lowest resistivity of 2.77 × 10−3 Ω cm within the present experiment at a carrier concentration of 1.38 × 1020 cm−3 and a Hall mobility of 16.6 cm2/Vs. The optical band gap energy shifted to higher energies and the transmittance at the blue range was improved dramatically as compared with similar amorphous IZO films. 相似文献