A high temperature reduction cleaning (HTRC) process: a novel method for conductivity recovery of yttrium-doped barium zirconate electrolytes

Han, Donglin; Iihara, Junji; Uemura, Shigeaki; Kazumi, Kenji; Hiraiwa, Chihiro; Majima, Masatoshi; Uda, Tetsuya

doi:10.1039/c6ta03552c

Cited by 37 publications

(30 citation statements)

References 31 publications

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“…All the samplesw ere prepared by sintering at 1500 8CinO 2 for 10 h. The datao f pure BZY20 sintered at 1600 8Ci nO 2 for 24 hisa lso plottedf or comparison. [36] The electrical conductivity is influenced by the annealing in hydrogen and the consequentr emovalo fn ickel and copper. It was difficult to determine whether the spectrum was similart oC uo rC u 2 O. However,b ecause the spectrums hifted towards the low energy side, the oxidation state of the Cu cations was definitely reduced.…”

Section: Transport Numbersmentioning

confidence: 99%

“…Although some researchers have reported degradationo ft he electrical conductivity after the addition of ZnO [12,[17][18][19] or NiO, [35][36][37] there is insufficient concern among researchers on the negative effect of sintering additives on the electrical properties. Although some researchers have reported degradationo ft he electrical conductivity after the addition of ZnO [12,[17][18][19] or NiO, [35][36][37] there is insufficient concern among researchers on the negative effect of sintering additives on the electrical properties.…”

Section: Introductionmentioning

confidence: 99%

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Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

et al. 2018

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Y-doped BaZrO (BZY) is currently the most promising proton-conductive ceramic-type electrolyte for application in electrochemical devices, including fuel cells and electrolyzer cells. However, owing to its refractory nature, sintering additives, such as NiO, CuO, or ZnO are commonly added to reduce its high sintering temperature from 1600 °C to approximately 1400 °C. Even without deliberately adding a sintering additive, the NiO anode substrate provides another source of the sintering additive; during the co-sintering process, NiO diffuses from the anode into the BZY electrolyte layer. In this work, a systematic study of the effect of NiO, CuO, and ZnO on the electroconductive properties of BaZr Y O (BZY20) is conducted. The results revealed that the addition of NiO, CuO, or ZnO into BZY20 not only degraded the electrical conductivity but also resulted in enhancement of the hole conduction. Removal of these sintering additives can be realized by post-annealing in hydrogen at a mild temperature of 700 °C, but it is kinetically very slow. Therefore, the addition of NiO, CuO, and ZnO is detrimental to the electroconductive properties of BZY20, and significantly restrict its application as an electrolyte. The development of new sintering additives, new anode catalysts, or new methods for preparing BZY electrolyte-based cells is urgently needed.

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Section: Transport Numbersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

et al. 2018

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“…The proposed mechanism for the solid state reactive sintering is described shortly 31 : Upon decomposition of the barium carbonate precursor, BaO and NiO begin to react at about 1100°C, producing a liquid phase. 31,[48][49][50] In that case, Ni enters the BZY lattice in oxidizing atmosphere and exsolves in reducing conditions. Because of their smaller size (compared to Y 3+ ), Ni 2+ ions first diffuse into the BaZrO 3 grains, with charge compensation being Atmosphere was dry 4% H 2 , balance Ar, identical to above BZY and BZCY experimental conditions.…”

Section: Sample Preparation Using Niomentioning

confidence: 99%

“…When the temperature increases, the BaZrO 3 phase starts to form. [48][49][50] It is important to highlight this difference in mechanism, to exclude the possible effect of NiO exsolution as a factor influencing the lattice parameter in the previously described experiments. Data collected upon cooling.…”

Section: Sample Preparation Using Niomentioning

confidence: 99%

Chemical expansion in BaZr_0.9−xCe_xY_0.1O_3−δ(x= 0 and 0.2) upon hydration determined by high‐temperature X‐ray diffraction

et al. 2017

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Understanding the strain from chemical expansion of proton‐conducting ceramics is crucial to prevent their failure under operating conditions. BZY10 (BaZr0.9Y0.1O3−δ) and BZCY72 (BaZr0.7Ce0.2Y0.1O3−δ) were studied using high‐temperature X‐ray diffraction (HT‐XRD) in moist and dry reducing atmosphere in order to prevent the competition with the oxidation reaction. Both powder and dense specimens were investigated and similar lattice parameters were obtained, demonstrating that the data were recorded on samples that were in equilibrium with the surrounding environment. Two sets of experiments were performed. In the first one, the sample was hydrated in situ in the XRD chamber at high temperature and diffraction data were collected during cooling. For the second set, the samples were pre‐hydrated ex situ in an autoclave and the XRD patterns were recorded during heating under dry conditions. As expected, lattice parameters were larger for the hydrated samples, due to hydration chemical expansion. The chemical expansion was also found to be larger with the presence of Ce. Finally, larger concentrations of protonic defects were present in the lattice of the ex situ pre‐hydrated samples compared with the in situ hydrated samples.

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“…Among all the electrolyte materials, proton conductors are regarded as potential electrolyte candidates for intermediate temperature SOFCs and the research in this field has been flourishing in the past few decades , . In the community of proton‐conducting oxides, BaZrO 3 ‐based materials are intensively studied as they possess good chemical stability that is critical for practical application, and the Y‐doped BaZrO 3 (BZY) ceramic oxide is the most used material in the BaZrO 3 family for proton‐conducting SOFCs, due to its high bulk conductivity . After tackling its processing difficulties as an electrolyte, the study on the cathode for BZY‐based cells now becomes the hot topic in the community , .…”

Section: Introductionmentioning

confidence: 99%

LaNi_0.6Fe_0.4O_3−δ as a Promising Cathode for Stable Proton‐conducting Solid Oxide Fuel Cells

Chen

Dai

et al. 2018

Fuel Cells

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A cobalt‐free material, LaNi0.6Fe0.4O3–δ (LNF), was applied as a potential cathode for solid oxide fuel cells (SOFCs) using chemically stable BaZr0.8Y0.2O3–δ (BZY20) electrolyte for the first time. LNF was synthesized, and this material showed a good compatibility with BZY20 at high temperatures. The anode supported BZY20 cell with the LNF cathode was fabricated and tested, which showed a decent cell performance of 217, 107, and 46 mW cm−2 at 700, 650, and 600 °C, respectively. This fuel cell performance was significantly higher than that for the cells using cobalt‐free cathode and BaZrO3‐based electrolyte in literature reports. Furthermore, the polarization resistance of the LNF cathode was restricted to 0.15 Ω cm2 at 700 °C, which was quite small and even can be compared with that for some cobalt‐containing cathodes for BaZrO3‐based cells. These experimental results indicate LNF could be an alternative and promising cathode for proton‐conducting cells with BaZrO3‐based ceramic electrolyte, providing an alternative route for choosing and designing their cathode materials.

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A high temperature reduction cleaning (HTRC) process: a novel method for conductivity recovery of yttrium-doped barium zirconate electrolytes

Abstract: A novel high temperature reduction cleaning (HTRC) process to recover the electrical conductivity of Y-doped barium zirconate electrolytes from Ni contamination.

Cited by 37 publications

References 31 publications

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

Chemical expansion in BaZr_0.9−xCe_xY_0.1O_3−δ(x= 0 and 0.2) upon hydration determined by high‐temperature X‐ray diffraction

LaNi_0.6Fe_0.4O_3−δ as a Promising Cathode for Stable Proton‐conducting Solid Oxide Fuel Cells

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A high temperature reduction cleaning (HTRC) process: a novel method for conductivity recovery of yttrium-doped barium zirconate electrolytes

Abstract: A novel high temperature reduction cleaning (HTRC) process to recover the electrical conductivity of Y-doped barium zirconate electrolytes from Ni contamination.

Cited by 37 publications

References 31 publications

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

Detrimental Effect of Sintering Additives on Conducting Ceramics: Yttrium‐Doped Barium Zirconate

Chemical expansion in BaZr0.9−xCexY0.1O3−δ(x= 0 and 0.2) upon hydration determined by high‐temperature X‐ray diffraction

LaNi0.6Fe0.4O3−δ as a Promising Cathode for Stable Proton‐conducting Solid Oxide Fuel Cells

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Chemical expansion in BaZr_0.9−xCe_xY_0.1O_3−δ(x= 0 and 0.2) upon hydration determined by high‐temperature X‐ray diffraction

LaNi_0.6Fe_0.4O_3−δ as a Promising Cathode for Stable Proton‐conducting Solid Oxide Fuel Cells