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1.
Vedat Sarıboğa Hasan Özdemir M.A. Faruk Öksüzömer 《Journal of the European Ceramic Society》2013,33(8):1435-1446
La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) materials are synthesized with a fast and facile cellulose templating method for the first time and characterized by XRD, EIS, Archimedes method and SEM–EDS. LSGM powders with a phase purity of 91.7 mol% are obtained after the calcination at 1300 °C for 12 h. SEM–EDS results indicate possible decomposition and reconstruction of the LSGM phase due to the diffusion of Sr-rich species to the grain boundaries for the sample sintered at 1500 °C for 6 h. Maximum conductivity value is found to be 4.2 × 10?2 S cm?1 at 800 °C for the sample calcined at 1300 °C for 12 h and sintered at 1400 °C for 6 h. Phase purity, stability and relative density are the important factors for obtaining high performance LSGM electrolytes. Therefore, cellulose templating method is a promising candidate for the preparation of LSGM electrolytes. 相似文献
2.
《Journal of the European Ceramic Society》2017,37(15):4751-4761
How to obtain dense La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) electrolyte at low sintering temperature (<1300 °C) is a challenge to improve solid oxide fuel cell (SOFC) performance at intermediate operation temperature. In this study, a double-layer design method for vacuum cold spray (VCS) prepared-LSGM electrolyte assisted with two-step sintering at a low temperature was proposed. The sintering behavior of VCS deposited LSGM layers at 1200 °C was investigated. The LSGM layers became denser in most regions except the appearance of some cracks. Subsequently, the effect of a second LSGM layer on the sintered top layer was studied to block cracks. Results showed that the co-sintered layer with a thickness of approximately 5 μm presented a maximum open circuit voltage of ∼0.956 V at 650 °C and a maximum power density of 592 mW/cm2 at 750 °C. Result indicates that the sintering assisted VCS is a promising method to prepare the LSGM electrolyte applied in intermediate temperature SOFCs. 相似文献
3.
Alberto Lapina Shuai Li Bill Bergman Zhe Zhao 《Journal of the European Ceramic Society》2012,32(10):2325-2331
A two-step doping strategy was applied to the synthesis of La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM1020) powder by a gel combustion method. The Mg-doped LaGaO3 powder was prepared in the first step, and Sr incorporation in the Mg-doped LaGaO3 powder was done in the second step to obtain the final LSGM1020 powder. The two-step procedure is effective in preparing higher purity powders than the traditional one-step procedure. Rietveld refinement of X-ray powder diffraction (XRD) patterns shows that incorporation of Mg in LaGaO3 in the first step enlarges the LaGaO3 lattice: this facilitates the incorporation of Sr in the second doping step and thus high purity powder is obtained. Relatively phase pure LSGM1020 powder with only 3.1% of LaSrGaO4 was obtained after calcination at 1300 °C for 5 h. Therefore, the two-step doping strategy is an effective procedure for the preparation of LSGM powders with high Sr- and Mg-doping levels. 相似文献
4.
Wandee Onreabroy Komane Papato Gobwute Rujijanagul Kamonpan Pengpat Tawee Tunkasiri 《Ceramics International》2012
M-type strontium ferrites, Sr0.8La0.2Fe12O19 have been synthesized by conventional ceramic process. The effects of lanthanum addition and sintering temperature on microstructures and magnetic properties of SrFe12O19 and Sr0.8La0.2Fe12O19 samples were investigated. Microstructural analysis of the SrFe12O19 and Sr0.8La0.2Fe12O19 specimens, sintered at different temperatures revealed that average grain sizes of SrFe12O19 ferrites were larger than that of Sr0.8La0.2Fe12O19 ferrite and increased with increasing sintering temperature. The X-ray diffraction (XRD) results confirmed the strontium hexagonal ferrite phase of SrFe12O19 and Sr0.8La0.2Fe12O19 compounds. A maximum coercivity value of 4850 Oe and maximum saturation magnetization value of 102 emu/g were obtained for the SrFe12O19 ferrite sintered at 1150 °C and for the SrFe12O19 and Sr0.8La0.2Fe12O19 ferrites sintered at 1300 °C, respectively. The remanence (Mr) of Sr0.8La0.2Fe12O19 sample sintered at 1200 °C possesses the maximum value of 60 emu/g. 相似文献
5.
《Ceramics International》2017,43(8):6329-6332
La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) was synthesized by a high temperature solid-state reaction. The crystal structure, relative density and electrical conductivity were measured with XRD, Archimedes method, and Van Der Pauw DC four-probe method. A limiting current oxygen sensor based on LSGM as both solid electrolyte and dense diffusion barrier was prepared by a Pt paste bonding method. The results show that LSGM has pure perovskite structure (cubic symmetry with space group of Pm-3m (No.221)), high density (relative density is 97.6%) and electrical conductivity (0.18 S∙cm−1 at 1073 K). The sensor works optimally over temperature range of 973‒1123 K and oxygen concentration of 1.92%‒21%. The operating voltage ranges from 0.67 to 0.98 V. The limiting current is in proportion to oxygen concentration. The sensor has the highest sensitivity at 1123 K and low measurement error of less than 4%. 相似文献
6.
《Ceramics International》2016,42(3):3797-3807
HfB2 powders were synthesized via a borothermal reduction route from mechanically activated HfCl4 and B powder blends. Mechanical activation of the powder blends was carried out for 1 h in a high-energy ball mill using hardened steel vial and balls. Mechanically activated powders were subsequently annealed at 1100 °C for 1 h under Ar atmosphere. Then, purification processes such as washing with distilled water and leaching in HCl solution were applied for the elimination of the undesired boron oxide (B2O3) phase and the probable Fe impurity. The effect of boron amount on the microstructure of the resultant powders was investigated. The boron amount in the starting blends plays an important role in the formation of the HfO2 phase. HfB2 powders without any detectable HfO2 were prepared by adding 20 wt% excess amount of boron. Microstructural analyses of the mechanically activated, annealed and purified powders were performed using X-ray diffractometer (XRD), particle size analyzer (PSA), stereomicroscope (SM), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and transmission electron microscope (TEM). 相似文献
7.
Two kinds of Ce0.8Gd0.2O2?δ pellets were synthesized by a solid-state reaction using two types of commercial CeO2 and Gd2O3. In contrast to previous reports, pellets with a sintered density of 99% at 1300 °C were obtained regardless the powder used. Mechanochemical activation of the starting materials by 7 h of high energy milling, which resulted in particles several tens of nanometer in size, was effective in reducing the sintering temperature. Ce0.8Gd0.2O2?δ pellets could be synthesized by direct sintering without calcination due to the homogeneous distribution of fine starting materials. The final phase was confirmed by the ionic conductivity, X-ray diffraction patterns and lattice parameters. 相似文献
8.
Meichao Peng Xiaoliang Shi Zhiwei Zhu Mang Wang Qiaoxin Zhang 《Ceramics International》2012,38(3):2027-2033
In this article, Ti/TiC/SiC/Al powder mixtures with molar ratios of 4:1:2:0.2 were high energy ball-milled, compacted, and heated in vacuum with various schedules, in order to reveal the effects of temperature, soaking time, thickness of the compacts, and carbon content on the purity of the sintered compacts. X-ray diffraction and scanning electron microscopy were employed to investigate the phase purity, particle size and morphology of the synthesized samples. It was found that the Ti3SiC2 content nearly reached 100 wt.% on the surface layer of the sintered compacts prepared in the temperature range from 1350 °C to 1400 °C for 1 h. Powder containing 91 wt.% Ti3SiC2 was successfully synthesized by heating 6 mm green compacts of 4Ti/1TiC/2SiC/0.2Al at 1380 °C for 1 h in vacuum. The excessive carbon content failed to improve the purity of Ti3SiC2 powder. TiC phase was the main impurity in the formation process of Ti3SiC2. 相似文献
9.
《Ceramics International》2017,43(2):2039-2045
Sub-micron sized TiB2 ceramic powders were prepared via self-propagating high-temperature synthesis (SHS) followed by HCl leaching at different temperatures. Purified powders obtained using optimum process parameters were consolidated by field assisted sintering technology/spark plasma sintering (FAST/SPS) technique. Phase and microstructural analyses of both the powder and sintered samples were carried out by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The chemical analyses and particle size measurements of the specimen were conducted by inductively coupled plasma-mass spectrometry (ICP-MS) and dynamic light scattering (DLS) techniques. The final properties of the sintered sample were determined in terms of density and microhardness. The effects of different HCl leaching temperatures on the formation, microstructure, particle size, purity and sintering behavior of the SHS-produced TiB2 powders were investigated. The SHS reaction of TiO2-B2O3-Mg powders as a starting mixture yielded MgO, Mg3(BO3)2 and Mg beside the desired phase TiB2. All three magnesium containing by-products were completely removed by performing hot HCl leaching. TiB2 powders after SHS reaction and leaching with 9.3 M HCl for 30 min at 80 °C revealed a minimum purity of 98.4% and a homogenous particle size distribution with an average particle size of 536 nm. In the ultimate SPS experiment which was conducted at 1500 °C for 5 min under a pressure of 50 MPa, a relative density of 94.9% and a micro-hardness value of 24.56 GPa were achieved. 相似文献
10.
Nanocrystalline (Ti0.8Zr0.2)C powder consisting in grains of about 200 nm in diameter obtained by mechanical alloying was sintered by a spark plasma sintering (SPS) process without the addition of any binder phase. The microstructure, Vickers micro hardness and density in relation to the sintering time and temperature are carefully described. The most suitable sintering condition under pressure of 50 MPa is 1650 °C for 5 min. In this sintering condition, the hardness can reach 2760 Hv and the relative density can reach 98%. 相似文献
11.
《Ceramics International》2015,41(8):9686-9691
A novel solid state reaction was adopted to prepare Sm0.2Ce0.8O1.9 (SDC) powder. A mixed oxalate Sm0.2Ce0.8(C2O4)1.5·2H2O was synthesized by milling a mixture of cerium acetate hydrate, samarium acetate hydrate, and oxalic acid for 5 h at room temperature. An ultra-fine SDC powder with the primary particle size of 5.5 nm was obtained at 300 °C. The ultra-low temperature for the formation of SDC phase was due to the atomic level mixture of the Sm3+ and Ce4+ ions. The crystal sizes of SDC powders at 300 °C, 550 °C, 800 °C, and 1050 °C were 5.5 nm, 11.4 nm, 24.1 nm and 37.5 nm, respectively. The sintering curves showed that the powder calcined at lower temperature was easier to be sintered owning to its smaller particle size. A solid oxide electrolytic cell (SOEC), comprising porous La0.8Sr0.2Cu0.1Fe0.9O3−δ (LSCF) for substrate, LSCF–SDC for active electrode, SDC for electrolyte, and LSCF–SDC for symmetric electrode, was fabricated by dip-coating and co-sintering techniques. An extremely dense SDC film with the thickness of 20 μm was obtained at only 1200 °C, which was about 100–300 °C lower than the literatures׳ reports. The designed SOEC was proved to work effectively for decomposing NO (3500 ppm, balanced in N2), 80% NO can be decomposed at 600 °C. 相似文献
12.
《Journal of the European Ceramic Society》2007,27(2-3):689-693
Tetragonal ZrO2 polycrystalline (TZP) composites with 2 wt.% Al2O3 and co-stabilised with 1 mol% Y2O3 and (4, 6 or 8) mol% CeO2 were sintered at 1450 °C for 20 min in a single mode 2.45 GHz microwave furnace. For comparison, conventional sintering was performed in air at 1450 °C for 20 min. The starting powder mixture was obtained by a suspension coating technique using yttrium nitrate, cerium nitrate and pure m-ZrO2 nanopowder. Fully dense material grades were obtained by both sintering methods. The influence of the composition and the sintering methods on the final phase composition and microstructure were investigated by X-ray diffraction and scanning electron microscopy. Finer and more uniform microstructures were observed in the microwave sintered ceramics when compared to the conventionally sintered samples. The fracture toughness increases with decreasing stabiliser content, whereas a reverse relation was found for the Vickers hardness. Comparable toughness and hardness values were obtained for the microwave and conventionally sintered samples. 相似文献
13.
Atanu Dutta Jayanta Mukhopadhyay R.N. Basu 《Journal of the European Ceramic Society》2009,29(10):2003-2011
Nanocrystalline SOFC cathode materials of perovskite family, La1?xSrxM1?yCoyO3, where 0 < x ≤ 0.5, 0 < y ≤ 0.8 (M is transitional metal = Mn or Fe), have been synthesized at a relatively low temperature by combustion synthesis using alanine as a novel fuel. Detailed X-ray powder diffraction analyses show 47–96% phase purity in the as-synthesized powder and upon calcination at ~825 °C single-phase material is obtained wherein the nanocrystallinity (crystallite size ~19–24 nm) is retained. Densification studies of the materials are carried out within 900–1100 °C. The coefficient of thermal expansion (CTE) of these cathodes is measured. Electrical conductivity of the cathodes sintered at different temperatures are measured in the temperature range 700–900 °C and correlated with the density of the sintered materials. The electrochemical performances of Ni-YSZ anode-supported SOFC having YSZ electrolyte (~10 μm) with CGO interlayer (~15 μm) are studied with the developed cathodes in the temperature range 700–800 °C using H2 as fuel and oxygen as oxidant. Highest current density of ~1.7 A/cm2 is achieved during testing at 800 °C measured at 0.7 V with a cathode composition of La0.5Sr0.5Co0.8Fe0.2O3. Precipitation of nanocrystalline grains over the core grains in porous microstructure of this cathode might be one of the reasons for such high cell performance. 相似文献
14.
Solid solutions of Sr and Mg doped lanthanum-gallate (LSGM) with addition of 3 and 5 at% of cobalt and nickel at the B-site in ABO3 perovskite structure were obtained using citrate sol–gel method. The synthesized powders were calcined at 900 °C and then finally sintered at 1450 °C for only 2 h, which resulted in approximately 95% density. Impedance spectroscopy was utilized for electrical characterization in the temperature range 200–600 °C. The activation energies calculated from impedance spectra for bulk and grain boundary conductivities were decreased by the addition of transition metals (Co and Ni) and subsequently the conductivity was increased. Two different regions were clearly distinguished in the plots ln(σT) vs. 10,000/T for grain boundary conductivities, indicating changes in the mechanism of charge transport with the temperature. It is concluded that addition of cobalt above 5 at% in the LSGM prepared by citrate sol–gel method does not enhance the electrolytic properties of LSGM. XRD results suggested possible coexistence of two perovskite crystalline phases in nickel doped samples. However, it is still more favorable for use in IT-SOFC applications than cobalt since it has less influence on the electrolytic domain of LSGM. 相似文献
15.
《Journal of the European Ceramic Society》2006,26(12):2357-2364
Strontium and magnesium doped lanthanum gallate La0.85Sr0.15Ga0.85Mg0.15O3−δ (LSGM) oxygen ionic conducting ceramics were prepared by a steric entrapment synthesis (SES) method, which is a polymeric precursor synthesis method by using polyvinyl alcohol in aqueous solution. The perovskite LSGM phase formed essentially at a calcination temperature of 900 °C. Pure and single perovskite LSGM phase with high relative density of 97.1% was obtained after sintering at 1450 °C, while the relative density of the LSGM sample sintered at the same temperature by solid state reaction (SSR) method was 80.6% in present experiment. Comparing with SSR synthesis method, the sintering temperature by SES can be reduced at least 100 °C. Impedance spectra revealed that the grain-boundary resistivity of LSGM synthesized by SES was smaller than that by SSR method, and the conductivities of the samples by SES were higher than those by SSR method at all measuring temperatures. 相似文献
16.
《Journal of the European Ceramic Society》2007,27(2-3):801-805
The effect of small amounts (0.2–2.0 wt.%) of bismuth oxide on the sintering behavior and microstructural development of Ce0.9Gd0.1O1.95 (GDC) submicronized powders has been studied using XRD for the lattice parameter measurements, the constant heating rate (CHR) method in air to monitor the shrinkage kinetics of powder compacts, and scanning electron microscopy (SEM) to study the microstructure of the sintered samples. Sintering of GDC compacts was significantly improved by adding small amounts of Bi2O3 (≤2.0 wt.%), and samples of doped-GDC sintered at 1200–1400 °C for 2–4 h were dense bodies (98–99.5% of theoretical density). Measurements showed that the addition of Bi2O3 could reduce the sintering temperature by about 250–300 °C lower than that for undoped-GDC samples. A liquid phase-assisting mechanism was assumed as the main cause for the enhancement of the densification process. The average grain size of doped-GDC sintered samples grew with the increasing of Bi2O3 addition up to 1.0 wt.%, and then decreased indicating a poor wetting properties of the formed liquid phase. 相似文献
17.
《Journal of the European Ceramic Society》2005,25(6):919-925
A BaSnO3 powder with a crystallite size of 27.6 nm has been prepared through a hydrothermal reaction of a peptised SnO2·xH2O and Ba(OH)2 at 250 °C and the following crystallization of this hydrothermal product at 330 °C. The peptisation of the SnO2·xH2O gel is dependent on the pH value. Through peptisation the mean particle size of SnO2·xH2O in the aqueous solution has been decreased by a factor of 100 to 8 nm. A limited agglomeration in the sol-prepared powder has been observed under the microscope. The structure evolution and crystallisation behaviours of the sol-prepared powders were investigated by TG-DTA, IR and XRD. The BaSn(OH)6 phase in the as-prepared powder transforms into an amorphous phase at 260 °C, from which the BaSnO3 particles nucleate and grow with an increase in temperature. The single-phase BaSnO3 powder has been obtained at a temperature as low as 330 °C. This sol-prepared powder is more sinter-reactive than the gel-prepared powder and can be sintered to a ceramic with 90.7% of the theoretic density. 相似文献
18.
《Journal of the European Ceramic Society》2017,37(4):1681-1688
Lanthanide orthophosphate ceramics with monazite structure gained broad interest for several industrial applications. The crystallization processes, compressibility and sinterability of monazite-type lanthanum orthophosphate powder hydrothermally synthesized at 200 °C as well as mechanical properties of the sintered compacts were investigated. Based on a combination of thermo- and surface area analyses, X-ray diffraction as well as scanning electron microscopy studies it was found that the crystallization process occurs at ∼500 °C and the final crystallization of LaPO4 monoclinic phase takes place at 1400 °C. The sintered pellets are characterized by a density of 98% of theoretical density, a Vickers hardness of 5.7 ± 0.1 GPa and fracture toughness of 1.4 ± 0.1 MPa m0.5. 相似文献
19.
V-doped TiO2 nanoparticles were synthesized by sonochemical process using titanium isopropoxide as a titanium source, vanadyl acetylacetonate as a dopant source. Sonication was conducted using sonic horn operated at 20 kHz for 20 min until the completely precipitated product was reached. The as-synthesized precipitates with various vanadium dopant (1–5 mol %) were calcined at 500–1000 °C for 4 h. The relevant physical properties of the nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM). The anatase phase TiO2 nanoparticles can be synthesized by sonochemical process. Post calcinations process results in the anatase-to-rutile phase transformation and the enhancement in crystallinity with increasing temperature. The results also indicate good incorporation of V ions in TiO2 lattices and significant effect of V dopant on alternation of interplanar spacing of TiO2. 相似文献
20.
The structural and optical properties of terbium aluminum garnet (TAG) powder sintered (~1100 °C) in air, vacuum (~10?6 mbar) and with 70 W of unfocussed CW CO2 laser radiation, have been studied using X-ray powder diffraction (XRD), scanning electron microscopy (SEM/TEM), FTIR, optical absorption and photoluminescence techniques. Structural properties of TAG are found to be independent of the sintering procedure except that the pure TAG crystalline phase (Tb3Al5O12) is evolved in about 2 h in the case of laser sintering compared to 8 h needed in air sintering (by furnace) and 4 h needed in the case of vacuum furnace sintering. On the other hand, the absorption/emission intensity (300–600 nm region) of TAG samples sintered in vacuum is higher compared to that of laser/furnace sintering in air. 相似文献