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Yoshiyuki Yajima - One of the best experts on this subject based on the ideXlab platform.
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synthesis of mg al spinel powder via precipitation using ammonium bicarbonate as the precipitant
Journal of The European Ceramic Society, 2001Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:Abstract A precursor for Mg–Al spinel has been synthesized via the precipitation method, using ammonium bicarbonate as the precipitant. The precursor was composed of crystalline ammonium dawsonite hydrate [NH4Al(OH)2CO3·H2O] and hydrotalcite [Mg6Al2(CO3)(OH)16·4H2O] phases. The precursor converted to pure spinel phase at ∼900°C via two steps upon calcination: (i) decomposition of hydrotalcite at lower temperatures (400–800°C) and (ii) solid-state reaction between MgO (decomposed from hydrotalcite) and γ-Al2O3 (derived from NH4Al(OH)2CO3·H2O) at higher temperatures (>800°C). The effect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders were investigated.
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synthesis of mg al spinel powder via precipitation using ammonium bicarbonate as the precipitant
Journal of The European Ceramic Society, 2001Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:A precursor for Mg‐Al spinel has been synthesized via the precipitation method, using ammonium bicarbonate as the precipitant. The precursor was composed of crystalline ammonium dawsonite hydrate [NH4Al(OH)2CO3 .H2O] and hydrotalcite [Mg6Al2 (CO3)(OH)16 .4H2O] phases. The precursor converted to pure spinel phase at900C via two steps upon calcination: (i) decomposition of hydrotalcite at lower temperatures (400‐800C) and (ii) solid-state reaction between MgO (decomposed from hydrotalcite) and g-Al2O3 (derived from NH4Al(OH)2CO3 .H2O) at higher temperatures (>800C). The eAect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders were investigated. # 2001 Elsevier Science Ltd. All rights reserved.
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a wet chemical process yielding reactive magnesium aluminate spinel mgal2o4 powder
Ceramics International, 2001Co-Authors: Takayasu Ikegami, Toshiyuki Mori, Jong Heun Lee, Yoshiyuki YajimaAbstract:Abstract Ammonium carbonate was used as the precipitant to synthesize Mg–Al spinel precursors from a mixed solution of magnesium and aluminum nitrates. The precursor, composed of crystalline ammonium dawsonite hydrate [NH 4 Al(OH) 2 CO 3 ·H 2 O] and hydrotalcite [Mg 6 Al 2 (CO 3 )(OH) 16 ·4H 2 O] phases, transformed to pure spinel at ∼900°C via the decomposition of hydrotalcite at ∼400–800°C and a solid-state reaction between MgO (decomposed from hydrotalcite) and γ-Al 2 O 3 (derived from NH 4 Al(OH) 2 CO 3 ·H 2 O) at ∼800–900°C. Sinterability of the resultant spinel powders was evaluated by the constant-rate-of-heating sintering method. The effect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders was investigated. Spinel ceramics of ∼99% dense were produced by vacuum sintering at 1550°C for 2 h from the powder calcined at 1100°C for 2 h.
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co precipitation synthesis and sintering of yttrium aluminum garnet yag powders the effect of precipitant
Journal of The European Ceramic Society, 2000Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:Abstract YAG precursors were co-precipitated from a mixed solution of aluminum and yttrium nitrates using ammonia water and ammonium hydrogen carbonate as precipitants, respectively. Phase evolution of the precursors during calcination and Sinterability of the resultant YAG powders were compared between the two methods. The use of ammonia water produced a hydroxide precursor with an approximate composition of Al(OH) 3 ·0.3[Y 2 (OH) 5 (NO 3 )·3H 2 O] which transformed to pure YAG at about 1000°C via YAlO 3 phase. Severe agglomeration caused poor Sinterability of the resultant YAG powders. The use of ammonium hydrogen carbonate produced a carbonate precursor with an approximate composition of NH 4 AlY 0.6 (CO 3 ) 1.9 (OH) 2 ·0.8H 2 O. The precursor directly converted to pure YAG at about 900°C. The precursor was loosely agglomerated and the resultant YAG powders showed good dispersity and excellent Sinterability. For the same calcination temperature of 1100°C, YAG powders from the hydroxide precursor and the carbonate precursor densified to ∼81.2 and ∼99.8% of the theoretical, respectively, by vacuum sintering at 1500°C for 2 h.
Enrico Traversa - One of the best experts on this subject based on the ideXlab platform.
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synthesis strategies for improving the performance of doped bazro 3 materials in solid oxide fuel cell applications
Journal of Materials Research, 2014Co-Authors: Lei Bi, Enrico TraversaAbstract:Solid oxide fuel cells (SOFCs) offer an efficient energy conversion technology for alleviating current energy problems. High temperature proton-conducting (HTPC) oxides are promising electrolytes for this technology, since their activation energy is lower than that of conventional oxygen-ion conductors, enabling the operating temperature reduction at 600 °C. Among HTPC oxides, doped BaZrO3 materials possess high chemical stability, needed for practical applications. Though, poor Sinterability and the resulting large volume of highly resistive grain boundaries hindered their deployment for many years. Nonetheless, the recently demonstrated high proton conductivity of the bulk revived the attention on doped BaZrO3, stimulating research on solving the sintering issues. The proper selection of dopants and sintering aids was demonstrated to be successful for improving the BaZrO3 electrolyte Sinterability. We here briefly review the synthesis strategies proposed for preparing BaZrO3-based nanostructured powders for electrolyte and electrodes, with the aim to improve the SOFC performance. © Materials Research Society 2013.
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lowering grain boundary resistance of bazr0 8y0 2o3 δ with lino3 sintering aid improves proton conductivity for fuel cell operation
Physical Chemistry Chemical Physics, 2011Co-Authors: Emiliana Fabbri, Lei Bi, Enrico TraversaAbstract:A novel sintering additive based on LiNO3 was used to overcome the drawbacks of poor Sinterability and low grain boundary conductivity in BaZr0.8Y0.2O3−δ (BZY20) protonic conductors. The Li-additive totally evaporated during the sintering process at 1600 °C for 6 h, which led to highly dense BZY20 pellets (96.5% of the theoretical value). The proton conductivity values of BZY20 with Li sintering-aid were significantly larger than the values reported for BZY sintered with other metal oxides, due to the fast proton transport in the “clean” grain boundaries and grain interior. The total conductivity of BZY20–Li in wet Ar was 4.45 × 10−3 S cm−1 at 600 °C. Based on the improved Sinterability, anode-supported fuel cells with 25 μm-thick BZY20–Li electrolyte membranes were fabricated by a co-firing technique. The peak power density obtained at 700 °C for a BZY–Ni/BZY20–Li/La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF)–BZY cell was 53 mW cm−2, which is significantly larger than the values reported for fuel cells using electrolytes made of BZY sintered with the addition of ZnO and CuO, confirming the advantage of using Li as a sintering aid.
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chemically stable pr and y co doped barium zirconate electrolytes with high proton conductivity for intermediate temperature solid oxide fuel cells
Advanced Functional Materials, 2011Co-Authors: Emiliana Fabbri, Lei Bi, Hidehiko Tanaka, Daniele Pergolesi, Enrico TraversaAbstract:A chemically stable and highly proton-conductive electrolyte is developed by partially substituting the Zr site of Y-doped barium zirconate (BZY) with 10 mol% of Pr. Compared to BZY, BaZr0.7Pr0.1Y 0.2O3-δ (BZPY) shows improved Sinterability as revealed by dilatometric measurements and scanning electron microscopy (SEM) analysis. Dense samples are obtained after sintering at 1500°C for 8 h. Moreover, BZPY shows good chemical stability in the wide range of fuel-cell operating conditions. The larger density and the enhanced grain growth, compared to BZY, allow the volume content of grain boundaries, which generally show a high resistance for proton transport, to be reduced and, thus, a high proton conductivity can be achieved in the temperature range of interest for practical applications (above 10-2 Scm-1 at 600°C). The good Sinterability, chemical stability, and high conductivity of the BZPY electrolyte enabled the fabrication of single-cell prototypes based on a thin BZPY membrane by a simple and cost-saving co-pressing method. Electrochemical impedance spectroscopy (EIS) analysis performed during fuel-cell tests under open-circuit conditions confirms the good electrical performance of BZPY as electrolyte material. To improve the present fuel-cell performance adapted cathode materials for this BZPY electrolyte need to be developed. Pr and Y co-doped barium zirconate (BZPY) is a chemically stable electrolyte with high proton conductivity. The good Sinterability of the BZPY electrolyte allows the development of an anode-supported solid oxide fuel cell (SOFC) based on a thin BZPY proton conducting membrane. The performed fuel-cell tests confirm that BZPY is a promising electrolyte material for intermediate-temperature SOFC applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wei Liu - One of the best experts on this subject based on the ideXlab platform.
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samarium and yttrium codoped baceo3 proton conductor with improved Sinterability and higher electrical conductivity
ACS Applied Materials & Interfaces, 2014Co-Authors: Zhen Shi, Wenping Sun, Zhongtao Wang, Jing Qian, Wei LiuAbstract:Acceptor-doped barium cerate is considered as one of the state-of-the-art high temperature proton conductors (HTPCs), and the proton conductivity of such HTPCs is heavily dependent on the dopant. In this work, a codoping strategy is employed to improve the electrical conductivity and Sinterability of BaCeO3-based HTPC. BaCe0.8SmxY0.2–xO3−δ (0 ≤ x ≤ 0.2) powders are synthesized by a typical citrate–nitrate combustion method. The XRD and Raman spectra reveal all the compounds have an orthorhombic perovskite structure. The effects of Sm and/or Y doping on the Sinterability and electrical conductivity under different atmospheres are carefully investigated. The SEM results of the sintered BaCe0.8SmxY0.2–xO3−δ pellets indicate a significant sintering enhancement with increasing Sm concentration. BaCe0.8Sm0.1Y0.1O3−δ exhibits the highest electrical conductivity in hydrogen among the BaCe0.8SmxY0.2–xO3−δ pellets. Anode-supported BaCe0.8Sm0.1Y0.1O3−δ electrolyte membranes are also fabricated via a drop-coating pro...
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samarium and yttrium codoped baceo3 proton conductor with improved Sinterability and higher electrical conductivity
ACS Applied Materials & Interfaces, 2014Co-Authors: Zhen Shi, Wenping Sun, Zhongtao Wang, Jing Qian, Wei LiuAbstract:Acceptor-doped barium cerate is considered as one of the state-of-the-art high temperature proton conductors (HTPCs), and the proton conductivity of such HTPCs is heavily dependent on the dopant. In this work, a codoping strategy is employed to improve the electrical conductivity and Sinterability of BaCeO3-based HTPC. BaCe0.8Sm(x)Y(0.2-x)O(3-δ) (0 ≤ x ≤ 0.2) powders are synthesized by a typical citrate-nitrate combustion method. The XRD and Raman spectra reveal all the compounds have an orthorhombic perovskite structure. The effects of Sm and/or Y doping on the Sinterability and electrical conductivity under different atmospheres are carefully investigated. The SEM results of the sintered BaCe0.8Sm(x)Y(0.2-x)O(3-δ) pellets indicate a significant sintering enhancement with increasing Sm concentration. BaCe0.8Sm0.1Y0.1O(3-δ) exhibits the highest electrical conductivity in hydrogen among the BaCe0.8Sm(x)Y(0.2-x)O(3-δ) pellets. Anode-supported BaCe0.8Sm0.1Y0.1O(3-δ) electrolyte membranes are also fabricated via a drop-coating process, and the corresponding single cell exhibits desirable power performance and durability at low temperatures. The results demonstrate that BaCe0.8Sm0.1Y0.1O(3-δ) is a promising proton conductor with high conductivity and sufficient Sinterability for proton-conducting solid oxide fuel cells operating at reduced temperatures.
Takayasu Ikegami - One of the best experts on this subject based on the ideXlab platform.
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synthesis of mg al spinel powder via precipitation using ammonium bicarbonate as the precipitant
Journal of The European Ceramic Society, 2001Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:Abstract A precursor for Mg–Al spinel has been synthesized via the precipitation method, using ammonium bicarbonate as the precipitant. The precursor was composed of crystalline ammonium dawsonite hydrate [NH4Al(OH)2CO3·H2O] and hydrotalcite [Mg6Al2(CO3)(OH)16·4H2O] phases. The precursor converted to pure spinel phase at ∼900°C via two steps upon calcination: (i) decomposition of hydrotalcite at lower temperatures (400–800°C) and (ii) solid-state reaction between MgO (decomposed from hydrotalcite) and γ-Al2O3 (derived from NH4Al(OH)2CO3·H2O) at higher temperatures (>800°C). The effect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders were investigated.
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synthesis of mg al spinel powder via precipitation using ammonium bicarbonate as the precipitant
Journal of The European Ceramic Society, 2001Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:A precursor for Mg‐Al spinel has been synthesized via the precipitation method, using ammonium bicarbonate as the precipitant. The precursor was composed of crystalline ammonium dawsonite hydrate [NH4Al(OH)2CO3 .H2O] and hydrotalcite [Mg6Al2 (CO3)(OH)16 .4H2O] phases. The precursor converted to pure spinel phase at900C via two steps upon calcination: (i) decomposition of hydrotalcite at lower temperatures (400‐800C) and (ii) solid-state reaction between MgO (decomposed from hydrotalcite) and g-Al2O3 (derived from NH4Al(OH)2CO3 .H2O) at higher temperatures (>800C). The eAect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders were investigated. # 2001 Elsevier Science Ltd. All rights reserved.
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a wet chemical process yielding reactive magnesium aluminate spinel mgal2o4 powder
Ceramics International, 2001Co-Authors: Takayasu Ikegami, Toshiyuki Mori, Jong Heun Lee, Yoshiyuki YajimaAbstract:Abstract Ammonium carbonate was used as the precipitant to synthesize Mg–Al spinel precursors from a mixed solution of magnesium and aluminum nitrates. The precursor, composed of crystalline ammonium dawsonite hydrate [NH 4 Al(OH) 2 CO 3 ·H 2 O] and hydrotalcite [Mg 6 Al 2 (CO 3 )(OH) 16 ·4H 2 O] phases, transformed to pure spinel at ∼900°C via the decomposition of hydrotalcite at ∼400–800°C and a solid-state reaction between MgO (decomposed from hydrotalcite) and γ-Al 2 O 3 (derived from NH 4 Al(OH) 2 CO 3 ·H 2 O) at ∼800–900°C. Sinterability of the resultant spinel powders was evaluated by the constant-rate-of-heating sintering method. The effect of calcination temperature on particle morphology and Sinterability of the resultant spinel powders was investigated. Spinel ceramics of ∼99% dense were produced by vacuum sintering at 1550°C for 2 h from the powder calcined at 1100°C for 2 h.
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co precipitation synthesis and sintering of yttrium aluminum garnet yag powders the effect of precipitant
Journal of The European Ceramic Society, 2000Co-Authors: Ji Guang Li, Takayasu Ikegami, Toshiyuki Mori, Yoshiyuki YajimaAbstract:Abstract YAG precursors were co-precipitated from a mixed solution of aluminum and yttrium nitrates using ammonia water and ammonium hydrogen carbonate as precipitants, respectively. Phase evolution of the precursors during calcination and Sinterability of the resultant YAG powders were compared between the two methods. The use of ammonia water produced a hydroxide precursor with an approximate composition of Al(OH) 3 ·0.3[Y 2 (OH) 5 (NO 3 )·3H 2 O] which transformed to pure YAG at about 1000°C via YAlO 3 phase. Severe agglomeration caused poor Sinterability of the resultant YAG powders. The use of ammonium hydrogen carbonate produced a carbonate precursor with an approximate composition of NH 4 AlY 0.6 (CO 3 ) 1.9 (OH) 2 ·0.8H 2 O. The precursor directly converted to pure YAG at about 900°C. The precursor was loosely agglomerated and the resultant YAG powders showed good dispersity and excellent Sinterability. For the same calcination temperature of 1100°C, YAG powders from the hydroxide precursor and the carbonate precursor densified to ∼81.2 and ∼99.8% of the theoretical, respectively, by vacuum sintering at 1500°C for 2 h.
X S Zhao - One of the best experts on this subject based on the ideXlab platform.
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improving the Sinterability of ceo2 by using plane selective nanocubes
Journal of The European Ceramic Society, 2019Co-Authors: Xiong Dan, Chao Wang, Ya Liu, Xiaowei Cheng, Marco Fronzi, X S ZhaoAbstract:Abstract CeO2 nanocubes with (100) surface orientation are successfully synthesized and found to facilitate the Sinterability of CeO2 material. The CeO2 nanocubes show a much-improved Sinterability relative to CeO2 nanoparticles prepared by the conventional citric-nitrate method. The nanocubes can be successfully sintered at a relatively low temperature of 1200 °C without using any sintering aids. In contrast, a pellet using conventional CeO2 nano-powder obtained from the conventional citric-nitrate method can be densified only after sintering at 1400 °C, which is 200 °C higher than that for the CeO2 nanocube sintering, although the starting particle size of both CeO2 samples is similar. Density functional theory indicates that the surface energy of the (100) plane is significantly higher than that of the (111) plane, which is the more typical surface presentation of conventional CeO2 particles. This high surface energy allows fast growth of the CeO2 nanocubes during sintering, contributing to their improved Sinterability.
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exploring the role of nio as a sintering aid in bazr0 1ce0 7y0 2o3 δ electrolyte for proton conducting solid oxide fuel cells
Journal of Power Sources, 2018Co-Authors: Bin Wang, Lei Bi, X S ZhaoAbstract:Abstract NiO is used as a sintering aid to modify BaZr0.1Ce0.7Y0.2O3-δ by an external addition method and by an internal doping strategy to improve the Sinterability of BaZr0.1Ce0.7Y0.2O3-δ. In both cases, the modified BaZr0.1Ce0.7Y0.2O3-δ materials show an improved Sinterability compared with the original BaZr0.1Ce0.7Y0.2O3-δ. However, doping BaZr0.1Ce0.7Y0.2O3-δ with NiO to form BaZr0.1Ce0.66Ni0.04Y0.2O3-δ is found to be an effective strategy to significantly improve the electrolyte properties. The BaZr0.1Ce0.66Ni0.04Y0.2O3-δ sample shows a high density and large grain size after sintering at a relatively low temperature (1400 °C). Electrochemical studies reveal that the doping strategy offers a high proton conductivity in both the bulk and across grain boundaries. The conductivity of BaZr0.1Ce0.66Ni0.04Y0.2O3-δ sintered at 1400 °C is observed to be higher than that of BaZr0.1Ce0.7Y0.2O3-δ sintered at 1600 °C. With BaZr0.1Ce0.66Ni0.04Y0.2O3-δ as the electrolyte, a proton-conducting solid oxide fuel cell displays a large peak power density of 477 mW cm-2 at 600 °C and a high electrolyte membrane conductivity of 6.3 × 10−3 S cm−1.