Feature: Functional Ceramics for Energy Conversion and Storage Devices: Full paper
Feature: Functional Ceramics for Energy Conversion and Storage Devices: Express letter
Feature: Functional Ceramics for Energy Conversion and Storage Devices: Special Article-Invited Review
Feature: Functional Ceramics for Energy Conversion and Storage Devices: Full papers
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Wei-Ja SHONG, Chien-Kuo LIU, Peng YANG, Ruey-Yi LEE, Kin-Fu LIN
2017 Volume 125 Issue 4 Pages
202-207
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Various compositions of mixture of silver (Ag) and nickel oxide (NiO) powders are studied for use as a cathode contact material in solid oxide fuel cell stacks. The addition of NiO is intended to mitigate Ag evaporation and maintain low resistivity of the contact material during stack operation. It is found that the mixture in the form of pellets consisting of 20 mol % Ag and 80 mol % NiO can yield acceptable area specific resistance (ASR) 2.24 mΩ cm
2 at 800°C with reduced weight loss. However, in the steel/Ag–NiO paste/steel assemblies prepared with 30–50 mol % Ag in mixed powders, each paste containing 64 wt % mixed powder, high ASR values of ∼100–200 mΩ cm
2 after 1552 h thermal exposure at 800°C are observed. The low resistivity of the pellet with 20 mol % Ag is attributed to the formation of effective conducting pathways by complete sintering of the densely packed Ag particles through the pressing process in producing the pellets. For the steel/Ag–NiO paste/steel assemblies, Ag particles are scattered within the Ag–NiO layer and cannot readily get sintered. It is found that the resistance of Ag–NiO mixture critically depends on the mass concentration of Ag powder.
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Hirofumi SUMI, Hiroyuki SHIMADA, Yuki YAMAGUCHI, Toshiaki YAMAGUCHI
2017 Volume 125 Issue 4 Pages
208-212
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Metal-supported solid oxide fuel cells (SOFCs) are expected to lower operating temperature and improve reliability. The residual crushing strength and electrical conductivity of porous metallic nickel microtubes were higher than those of nickel-gadolinia-doped ceria (Ni-GDC) cermets. The maximum power density of the metal-supported microtubular SOFC with GDC electrolyte was approximately three times higher than that of a conventional anode-supported microtubular SOFC with yttria-stabilized zirconia electrolyte at a relatively low temperature of 550°C. The metal-supported microtubular SOFCs have a potential to be applied not only in stationary devices, such as residential combined heat/power systems, but also in portable power sources and vehicles.
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Fumitada IGUCHI, Shoma ONUKI, Makoto SHIMIZU, Tatsuya KAWADA, Hiroo YU ...
2017 Volume 125 Issue 4 Pages
213-217
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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A feasible study for an in-situ stress evaluation method for solid oxide fuel cells based on Raman scattering spectroscopy was performed using two anode-supported cells with a cathode interlayer made from Samarium (Sm) doped ceria. Model cells with a dense cathode interlayer demonstrated a compressive stress of −100s MPa at room temperature, and the results were comparable to those from X-ray diffraction. Model cells with a porous interlayer showed complex stress conditions that deviated from in-plane stress due to their porosity, and the model cell was confirmed not to be suitable for this method. At high temperatures, compressive stress was found to decrease as temperature increased and was almost neutral at the operating temperatures of the fuel cell, with good replication. Hence, the feasibility of this method for model cells with a dense cathode interlayer was confirmed.
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Kazuki SHIMURA, Hanako NISHINO, Katsuyoshi KAKINUMA, Manuel E. BRITO, ...
2017 Volume 125 Issue 4 Pages
218-222
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Supplementary material
We have examined the long-term durability of a La
0.6Sr
0.4Co
0.2Fe
0.8O
3−δ (LSCF)–samaria-doped ceria (SDC) composite oxygen electrode with SDC interlayer for reversible solid oxide cells (R-SOCs). A symmetrical cell with the configuration: LSCF–SDC|SDC interlayer|yttria-stabilized zirconia (YSZ) electrolyte|SDC interlayer|LSCF–SDC, was operated at 900°C and a constant current density of 0.5 A cm
−2 with the top electrode as the anode (O
2 evolution). The IR-free overpotentials at both the anode and cathode were virtually constant during 5500 h of operation. The value of ohmic resistance at the anode side (
RA) increased slightly, whereas that at the cathode side (
RC) increased markedly. The
I–E performance of the bottom electrode (operated as the cathode), that was measured from −1.0 to 1.0 A cm
−2 every 1000 h, degraded specifically at high current densities. It was found that the thickness, pore size, and porosity in both electrodes were unchanged, but the distribution of the Sr component changed markedly at both the LSCF–SDC/SDC interlayer and SDC interlayer/YSZ interfaces. While the diffusion of the Sr component from the anode was limited within the SDC interlayer, the Sr component from the cathode reached the SDC interlayer/YSZ interface, which could increase the
RC, likely due to the formation of SrZrO
3. However, the diffusion rates of Sr were found to be noticeably slowed down at dense portions of the SDC interlayer. Hence, it is essential to prepare a dense, uniform SDC interlayer to improve both the durability and performance of R-SOCs.
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Toshihiro MORIGA, Ryota MINAKATA, Yutaro NOMURA, Hiroki ISHIKAWA, Kei- ...
2017 Volume 125 Issue 4 Pages
223-226
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Nb-substituted or Ta-substituted strontium titanates were synthesized by conventional solid-state reactions. For perovskite-type titanates, Sr
1−yTi
1−xM
xO
3, the lattice constant
a was found to increase with the amount of dopant (
x) added, to maximum values of 3.927 and 3.930 Å for M = Nb and Ta respectively, regardless of Sr deficiency (
y). X-ray diffraction studies revealed that the Ta-substituted strontium titanate possesses a wider stable region in its perovskite-type structure against the amount of added dopant (
x) and strontium deficiency (
y), compared with the Nb-substituted structure. Even in the single phase regions of SrTi
1−xM
xO
3 (M = Nb and Ta) perovskites, scanning electron microscopy images confirmed that after firing at 1500°C for 10 h some SrTi
0.9Ta
0.1O
3 grains showed strontium and tantalum enrichment and titanium dilution, whereas no inhomogeneity was found in SrTi
0.9Nb
0.1O
3. This cationic compositional fluctuation is consistent with the lower electrical conductivity of SrTi
0.9Ta
0.1O
3 compared with SrTi
0.9Nb
0.1O
3 at low temperatures.
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Kazuhiro KURATA, Yuichiro TOYOTA, Tsubasa SATO, Eiki NIWA, Katusmi SHO ...
2017 Volume 125 Issue 4 Pages
227-235
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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In order to evaluate potential of PrNi
1−xFe
xO
3−δ as new cathode material for solid oxide fuel cells, single phase preparation, crystal structure at various temperatures, thermal expansion property and electrical conduction behavior at high temperature were investigated. Single phase of PrNi
1−xFe
xO
3−δ (0.3 ≤
x ≤ 1.0) with orthorhombic distorted perovskite structure was successfully prepared by Pechini method. No structural phase transition was observed between room temperature and 1000°C in air. Linear thermal expansion coefficient was evaluated to be around 1.16 × 10
−5 K
−1, showing fair agreement with that of yttria-stabilized zirconia and gadolinia-doped ceria which were frequently employed as electrolyte material. Electrical conductivity of PrNi
1−xFe
xO
3−δ increased with increasing Ni content; however, the conductivity did not exceed that of LaNi
1−xFe
xO
3−δ. From the comparison of activation energy of variable range hopping conduction and Mössbauer spectroscopy between PrNi
1−xFe
xO
3−δ and LaNi
1−xFe
xO
3−δ, it was suggested that hole carrier concentration of PrNi
1−xFe
xO
3−δ was lower than that of LaNi
1−xFe
xO
3−δ owing to variation of valence of Pr ion.
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Yi-Xin LIU, Sea-Fue WANG, Yung-Fu HSU, Piotr JASINSKI
2017 Volume 125 Issue 4 Pages
236-241
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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In this study, La
0.8Sr
0.2Ga
0.8Mg
0.2O
3−δ (LSGM)-supported micro tubular solid oxide fuel cells (T-SOFCs) with two different configurations, one containing an LSGM–Ce
0.6La
0.4O
2−δ (LDC) bi-layer electrolyte (Cell A) and one containing an LDC–LSGM–LDC tri-layer electrolyte (Cell B), were fabricated using extrusion and dip-coating. After optimizing the paste formulation for extrusion, the flexural strength of the dense and uniform LSGM micro-tubes sintered at 1500°C was determined to be approximately 144 MPa. Owing to the insertion of an LDC layer between LSGM electrolyte and La
0.6Sr
0.4Co
0.2Fe
0.8O
3−δ (LSCF)–LSGM cathode, the ohmic resistances of Cell B were slightly larger than those of Cell A at the operating temperatures investigated, mainly because of interfacial resistance, but Cell B exhibited slightly lower polarization resistance than Cell A. The maximum power densities (MPDs) of Cell A were 0.25, 0.35, 0.43, and 0.47 W cm
−2 at 650, 700, 750, and 800°C, respectively, which are slightly larger than those of Cell B, i.e., 0.23, 0.33, 0.42, and 0.41 W cm
−2, respectively, owing to the facts that Cell A exhibited a slightly higher open-circuit voltage and a smaller R
t value. Cell A containing the LSGM (288 µm)–LDC (8 µm) bi-layer electrolyte can be operated at approximately 650°C with an MPD value of approximately 0.25 W cm
−2; however, a similarly structured single cell containing a Zr
0.8Sc
0.2O
2−δ (ScSZ) (210 µm) electrolyte need to be operated at 900°C, and one containing an Ce
0.8Gd
0.2O
2−δ (GDC; 285 µm)–ScSZ (8 µm) bi-layer electrolyte has to be operated at 700°C. Thus, the advantage of using LSGM as an electrolyte for micro T-SOFC single cells is apparent.
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Isao KAGOMIYA, Yuki HIROTA, Kyosuke TSUNEKAWA, Ken-ichi KAKIMOTO
2017 Volume 125 Issue 4 Pages
242-246
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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To investigate the influence of orthorhombic-based perovskite structures on oxygen permeation, this study focused on (Sm, Ca)FeO
3. The (Sm
1−xCa
x)FeO
3 (
x = 0.20, 025, 0.30) samples were prepared using a conventional solid-state reaction method. The relative density of the prepared samples was larger than 95%. All the prepared samples were orthorhombic perovskites with space groups of
Pbnm. The lattice volume decreased with increases in the Ca content. The tilt angles of the FeO
6 octahedral decreased with increases in the Ca content. The oxygen permeation flux
JO2 values increased and the activation energy
EJ for the
JO2 decreased with increases in the Ca content. The total conductivity σ
t value of the
x = 0.25 sample was highest among the three different Ca content samples, suggesting that the oxygen vacancy formation energy decreases with increases in the Ca content from
x = 0.20 to 0.30. Based on the investigation results, we assume that lower oxygen vacancy formation energy with doping with Ca ions is an important factor in improving oxygen permeation as well as ion conductive properties in the (Sm
1−xCa
x)FeO
3.
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Tomohiro ISHIYAMA, Haruo KISHIMOTO, Katherine DEVELOS-BAGARINAO, Katsu ...
2017 Volume 125 Issue 4 Pages
247-251
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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The perovskite-type proton conductor with the composition of BaZr
0.1Ce
0.7Y
0.1Yb
0.1O
3−δ (BZCYYb) has been reported to exhibit the highest proton conductivity among proton conductors. However, cerate-based perovskite materials such as BZCYYb are also known to react with carbon dioxide which causes phase decomposition through the formation of barium carbonate. This is a significant issue because chemical stability is an important property to enable these materials to be utilized for fuel cell applications. In this study, the chemical stability of BZCYYb was investigated in CO
2 or CO
2 + H
2 atmosphere, with or without nickel addition as sintering aid. Some nickel addition is assumed to occur from nickel diffusion in anode-support-type fuel cells. The enhancement of reactivity with carbon dioxide species by adding nickel into BZCYYb was attributed to barium enrichment at grain boundary regions and the formation of an impurity phase of Ba(Y
(1−x)Yb
x)
2NiO
5. Moreover, different decomposition reactions depending on the atmosphere have been inferred. In a pure CO
2 atmosphere, barium carbonate formation occurred without appearance of the CeO
2-based phase, in other words, without decomposition of the perovskite phase. On the other hand, in hydrogen-containing CO
2 atmosphere, both the barium carbonate and CeO
2-based phase were observed.
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Naohiro SHIMODA, Yusuke KOBAYASHI, Yutaka KIMURA, Go NAKAGAWA, Shigeo ...
2017 Volume 125 Issue 4 Pages
252-256
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Electrochemical synthesis of ammonia (NH
3) using a proton conducting solid electrolyte and nickel (Ni) cermet electrodes has been studied. As an electrolyte, BaCe
0.9Y
0.1O
3−δ (BCY) perovskite-type oxide was prepared by a co-precipitation method and its electrolyte pellet was synthesized by the sintering method with small amount of nickel oxide (NiO) as a sintering aid. The Ni–BCY cermet was employed as electrodes of anode and cathode. To evaluate the performance of this cell, electrochemical synthesis of NH
3 from dry nitrogen (N
2) and wet hydrogen (H
2) was conducted at 500°C. As a result, the maximum formation rate of NH
3 was 3.36 × 10
−10 mol s
−1 cm
−2 at the applied voltage of −0.2 V against open circuit voltage using the Ni–BCY|BCY(NiO)|Ni–BCY cell, and the Faradic efficiency was 0.63%. Durability test of NH
3 electrochemical synthesis from dry N
2 and wet H
2 revealed that current density of cell was relatively stable for 15 h but NH
3 formation rate was decreased slightly. In addition, using Ni–BCY based cell, NH
3 was successfully synthesized from dry N
2 and steam diluted argon with the applied voltage of −1.8 V at a rate of 2.79 × 10
−10 mol s
−1 cm
−2 and the Faradic efficiency was 0.15%. And this fabricated cell kept the high NH
3 formation rate during the long-term test at −2.0 V for 15 h.
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Hiroyuki SHIMADA, Toshiaki YAMAGUCHI, Hirofumi SUMI, Yuki YAMAGUCHI, K ...
2017 Volume 125 Issue 4 Pages
257-261
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Perovskite-type mixed protonic and oxide ionic conductors for electrolyte material of solid oxide fuel cells were investigated, focusing on BaZr
0.1Ce
0.7Y
0.1Yb
0.1O
3−δ (BZCYYb) due to its high ionic conductivity and chemical stability. BZCYYb and NiO-added BZCYYb were evaluated using electrolyte-supported cell (ESC) and anode-supported cell (ASC) samples. 2 wt.% NiO was solid solute into the BZCYYb, resulting in improvement in the sinterability and thermal-expansion behavior. The addition of NiO, however, lead to the deterioration of cell performance. Compared with the ESC, power density of the ASC was much higher due to thin electrolyte, whereas its open-circuit voltage (OCV) was lower. This is due to Ni diffusion from the NiO–BZCYYb anode into the BZCYYb electrolyte during high-temperature co-sintering process at 1350°C. From the results of OCV measurements, 0–2 wt.% NiO was considered to be dissolved in the BZCYYb electrolyte of the ASC, suggesting that controlling Ni diffusion during co-sintering process is essential to achieve higher-performance ASCs using BZCYYb.
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Jung Yoon SEO, Sung Nam LIM, Seung Bin PARK, Dae Soo JUNG
2017 Volume 125 Issue 4 Pages
262-267
Published: April 01, 2017
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A lithium-rich layered cathode material [0.4Li
2MnO
3·0.6Li(Mn
0.43Ni
0.36Co
0.21)O
2)] containing nanosized grains (50–100 nm) was prepared from an aqueous precursor solution via a sequential two-step process composed of ultrasonic spray pyrolysis and post-calcination. The microsized lithium-rich layered composites show a high initial discharge capacity of 251 mA h g
−1 at 0.1 C. The reversible capacities of 206 mA h g
−1 at 0.5 C and 189 mA h g
−1 at 1 C are obtained between 4.6 and 2.0 V. These are comparable to the values reported previously for these materials, without the need for doping or surface modification. The improved electrochemical performance may have resulted from the presence of nanosized grains, which can lead to an improvement in electronic and ionic transport, and the homogeneously dispersed Li
2MnO
3 phase in the LiMO
2 (M = Mn, Ni, Co) phase. These results suggest that spray pyrolysis is an effective technique for the preparation of multi-component composite materials and can be used to control the microstructure of the materials, ultimately improving the electrical performance.
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Atsushi SAKUDA, Tomonari TAKEUCHI, Masahiro SHIKANO, Koji OHARA, Katsu ...
2017 Volume 125 Issue 4 Pages
268-271
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Supplementary material
Solid solution of Li
2TiS
3 (Li
8/3Ti
4/3S
4) and Li
3NbS
4 were prepared using mechanochemical syntheses. The materials with cubic rock-salt structure were obtained over the full range of compositions (Li
(8+x)/3Ti
(4−4x)/3Nb
xS
4; 0 ≦
x ≦ 1). Lithium, titanium, and niobium randomly share the cationic site. Each material showed electrode activity and had a large reversible capacity of more than 350 mAh g
−1 with more than 3 electron process per composition formulas of Li
(8+x)/3Ti
(4−4x)/3Nb
xS
4.
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Naoki HAMAO, Kunimitsu KATAOKA, Junji AKIMOTO
2017 Volume 125 Issue 4 Pages
272-275
Published: April 01, 2017
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We investigated the Li-ion conductivity and crystal structure of the Ta-doped Li
7La
3M2O
12 (
M = Hf, Sn) samples. All of the Ta-doped samples exhibited a relatively high conductivity of ∼10
−4 S cm
−1 at room temperature, and the activation energies of Li
6.5La
3Hf
1.5Ta
0.5O
12 and Li
6.5La
3Sn
1.5Ta
0.5O
12, which were determined from the Arrhenius plots in measured temperature range, are
Ea = 0.400(6) and 0.451(1) eV, respectively. The crystal structure was analyzed by Rietveld method using powder X-ray diffraction data. From a view point of the Li–O polyhedral volume in unit cell, Li
6.5La
3Hf
1.5Ta
0.5O
12 has a most suitable Li-ion environment among the Li
7La
3M2O
12 (
M = Zr, Hf, Sn) compounds.
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Toyoki OKUMURA, Tomonari TAKEUCHI, Hironori KOBAYASHI
2017 Volume 125 Issue 4 Pages
276-280
Published: April 01, 2017
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Lithium-ion conductivity of Li
2.2C
0.8B
0.2O
3 pellet is 2.1 × 10
−6 S cm
−1 at 30°C after sintering at 450°C by spark-plasma sintering (SPS) process, which is about three times higher than the conductivity of the pellet sintered at 660°C in conventional furnace. The ionic resistance at grain boundary was especially minimalized by SPS process, which would be related to the grain-growth suppression under densification as confirmed by surficial SEM image. Improvement of charge–discharge capacity could be measured at all-solid-state lithium battery assembled by the SPS process (LiCoO
2–Li
2.2C
0.8B
0.2O
3 composite electrolyte/Li
2.2C
0.8B
0.2O
3/dry polymer/Li foil) compared with the same compositions of the battery assembled by conventional furnace sintering, which would be due to the enhancement of the ionic transfer at LiCoO
2/Li
2.2C
0.8B
0.2O
3 hetero interface as well as Li
2.2C
0.8B
0.2O
3/Li
2.2C
0.8B
0.2O
3 grain-boundary resistance.
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Naoya ISHIDA, Kazumasa SAKATSUME, Naoto KITAMURA, Yasushi IDEMOTO
2017 Volume 125 Issue 4 Pages
281-286
Published: April 01, 2017
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Lithium iron metasilicate, LiFeSi
2O
6, was synthesized via a hydrothermal route and was identified as the pyroxene structure with space group
C2/
c using the synchrotron X-ray diffraction. Galvanostatic charge and discharge tests showed that the large charge and discharge capacities were obtained for the carbon-LiFeSi
2O
6 composite prepared by planetary ball-milling. The 10 wt % carbon-LiFeSi
2O
6 composite delivered a specific discharge capacity of 174 mAh·g
−1 at 25°C in the voltage range from 1.5 to 4.8 V because of the enhancement of the electric conductivity. The valence state of iron was estimated by the X-ray Absorption Near Edge Structure spectra, where the oxidation states changed from charge to discharge state. The Galvanostatic Intermittent Titration measurement was applied for LiFeSi
2O
6 and carbon-LiFeSi
2O
6 composite, and then the improved Li
+ diffusion was derived from the fully electron supply by the enhanced electric conductivity.
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Shota AZUMA, Kota AIYAMA, Go KAWAMURA, Hiroyuki MUTO, Takanori MIZUSHI ...
2017 Volume 125 Issue 4 Pages
287-292
Published: April 01, 2017
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Li
2S–P
2S
5 (LPS) film was prepared using colloidal process by employing electrophoretic deposition (EPD) technique followed by warm pressing for advanced processing of all-solid-state lithium ion battery. LPS precursor film with positive surface charge was obtained from its suspension that was synthesized by liquid-phase shaking method. The homogeneous film with thickness of 10–100 µm was controllably prepared. Resulted LPS film exhibited high conductivity (1.98 × 10
−4 S cm
−1) at ambient temperature and significantly low activation energy (16.6 kJ mol
−1) compared with conventional LPS materials. Thus, good solid–solid interfacial contact can be obtained in the sulfide-based ionic conductor by employing EPD process followed by warm pressing.
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Shinya SUZUKI, Masaru MIYAYAMA
2017 Volume 125 Issue 4 Pages
293-298
Published: April 01, 2017
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As potential cathode materials for thin-film energy storage devices, Mn–Ni oxide nanosheets with the chemical composition H
0.46Mn
0.81Ni
0.19O
2 (M81N19) were prepared. Upon restacking in HNO
3 aqueous solution and re-exfoliation, the Mn–Ni oxide nanosheets produced the novel H
0.58Mn
0.81Ni
0.13O
2 (M81N13) nanosheets with vacancy defects. The chemical composition of the nanosheets was characterized using X-ray absorption spectroscopy, inductively coupled plasma atomic emission spectroscopy, and thermogravimetry. The sizes of the M81N19 and M81N13 nanosheets were compared, and no structural change was observed after Ni dissolution from the nanosheets. The optical properties, the local structure and the electrochemical properties when used as cathodes in Li-ion batteries of the M81N19 and M81N13 nanosheets, were compared.
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Mahunnop FAKKAO, Kazuki CHIBA, Yuta KIMURA, Takashi NAKAMURA, Toyoki O ...
2017 Volume 125 Issue 4 Pages
299-302
Published: April 01, 2017
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In this work, we directly observed the reaction distribution formed in a composite cathode of the all-solid-state lithium-ion battery (ASSLIB) LiCoO
2/Li
2.2C
0.8B
0.2O
3|Li
2.2C
0.8B
0.2O
3|PEO|Li during charging by using the two-dimensional X-ray absorption spectroscopy (2D-XAS) at Co
K-edge. The two-dimensional mapping of the state of charge in a composite cathode indicated that the reaction distribution was formed during charging process in the in-plane direction due to the disconnection in electron pathway at cracks. It was experimentally confirmed that the 2D-XAS technique was a useful tool for evaluating the reaction distribution in a composite cathode of an ASSLIB and investigating the influence factors for the formation of the reaction distribution.
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Takeo OKU, Yuya OHISHI, Atsushi SUZUKI, Yuzuru MIYAZAWA
2017 Volume 125 Issue 4 Pages
303-307
Published: April 01, 2017
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Effects of NH
4Cl addition to perovskite CH
3NH
3PbI
3 precursor solutions on photovoltaic properties were investigated. TiO
2/CH
3NH
3PbI
3(Cl)-based photovoltaic devices were fabricated by a spin-coating technique, and the microstructures of the devices were investigated by X-ray diffraction and scanning electron microscopy. Current density–voltage characteristics were improved by a small amount of Cl-doping, which resulted in improvement of the efficiencies of the devices. The structure analysis indicated formation of a homogeneous microstructure by NH
4Cl addition to the perovskite phase, and formation of PbI
2 was suppressed by the NH
4Cl addition.
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Kenjiro FUJIMOTO, Minoru GIBU, Yuki YAMAGUCHI, Akihisa AIMI, Keishi NI ...
2017 Volume 125 Issue 4 Pages
308-312
Published: April 01, 2017
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The thermoelectric properties of Ca
1−xBi
xMnO
3−δ sintered bodies prepared by the electrostatic spray deposition method and sintering technology were evaluated. Ca
0.95Bi
0.05MnO
3−δ showed the maximum power factor value of 230 µW·m
−1·K
−2 among Ca
1−xBi
xMnO
3−δ compounds at room temperature. From Seebeck coefficient, Hall coefficient and power generation efficiency measurements on CaMnO
3−δ and Ca
0.95Bi
0.05MnO
3−δ under high temperature, it was found that the power factor value of Ca
0.95Bi
0.05MnO
3−δ increased with temperature in the range of 300–873 K, and was 2 to 5 times higher than that of CaMnO
3−δ. The carrier concentration (
n = 5.9 × 10
20 cm
−3) of Ca
0.95Bi
0.05MnO
3−δ is two orders of magnitude higher than CaMnO
3−δ (
n = 7.1 × 10
18 cm
−3) at 300 K. The increase in carrier concentration contributed to higher conductivity, power factor and power generation density in the Bi-substituted compound. In thermoelectric performance evaluations, the power density reached 625 mW·cm
−2 for Ca
0.95Bi
0.05MnO
3−δ with a temperature difference of 444 K, an 11-fold increase compared to the parent compound CaMnO
3−δ (57 mW·cm
−2).
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Feature: Functional Ceramics for Energy Conversion and Storage Devices: Technical reports
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Byung-Koog JANG, Fan-Jie FENG, Keiko SUZUTA, Hidehiko TANAKA, Yoshitak ...
2017 Volume 125 Issue 4 Pages
326-332
Published: April 01, 2017
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High-temperature corrosion behavior of volcanic ash and artificial calcium-magnesium-aluminosilicate (CMAS) on sintered ytterbium monosilicate (Yb
2SiO
5), and the corrosion resistance of Yb
2SiO
5 as an environmental barrier coating, are investigated. Dense sintered Yb
2SiO
5 specimens were prepared using the spark plasma sintering method at 1400°C for 10 min. These specimens were subjected to a hot corrosive environment of molten Iceland volcanic ash and CMAS at 1400°C for 2, 12, and 48 h. Different corrosion phenomena, i.e., continuous reaction with CMAS and weak reaction with the volcanic ash, were observed. From the results of in-situ high temperature X-ray diffraction measurement and scanning electron microscope-energy dispersive X-ray spectrometry studies, Yb
2SiO
5 exhibits excellent resistance to volcanic ash but lacks resistance to CMAS attack.
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Chiyuki SATO, Yota KIMURA, Hiroshi YANAGI
2017 Volume 125 Issue 4 Pages
333-337
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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Bandgap-tunable (2.5 ≤
Eg ≤ 4.3 eV) amorphous Cd–Ga–O films with mobilities of ∼10 cm
2 V
−1 s
−1 were annealed in vacuum (∼10
−4 Pa), Ar, and O
2 atmospheres. The Cd concentrations ([Cd]/([Cd] + [Ga])) of 70, 50, and 20% films, with respective bandgap energies of ∼2.5, ∼3.0, and ∼4.0 eV, were employed for representative narrow, middle, and wide bandgap samples, respectively. The carrier concentrations of all of the annealed films, except those with a Cd concentration of 70% annealed in a vacuum and Ar, showed minimum values at annealing temperatures between 200 and 300°C. This was probably due to structural relaxation, which leads to low in-gap states. The threshold carrier concentrations for demonstrating high mobility (∼10 cm
2 V
−1 s
−1) were 10
18 cm
−3 for films with a Cd concentration of 70% and ≤10
17 cm
−3 for films with a Cd concentration of 50% films. O
2 annealing of films with a Cd concentration of 20% effectively decreased the carrier concentration to ∼ 10
15 cm
−3, with a Hall mobility of ∼3 cm
2 V
−1 s
−1, which is a distinctively high mobility for amorphous oxide with bandgap energy of ∼4 eV. The marked decreases in the carrier concentration and mobility of the Cd concentration of 20% film at 600°C with O
2 annealing were assumed to be due to the formation of microcrystalline Ga
2O
3.
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Yoshiteru ITAGAKI, Akinori HIRAOKA, Hiromichi AONO, Hidenori YAHIRO
2017 Volume 125 Issue 4 Pages
338-342
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
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Hydrogen permeation properties of Gd
0.1Ce
0.9O
x/BaCe
0.80Y
0.20O
3−δ (GDC/BCY) dual-phase membranes were evaluated. Nongalvanic hydrogen permeation was observed for 46 vol % GDC-containing BCY membranes: the permeation rate was 0.30 ml·min
−1·cm
−2 at 800°C. This is almost comparable to the reported value of Ni–BCY cermet (0.50 ml·min
−1·cm
−2). This nongalvanic hydrogen permeation unambiguously indicates that the BCY–GDC composite functions as a mixed proton–electron conductor in an H
2 reducing atmosphere. From a conductivity analysis, it was deduced that 46 vol % GDC/BCY possesses proton and electron conductivities comparable to the bulk states of BCY and GDC. The composite membrane was stable in an atmosphere switching between H
2 and air. TGA analysis indicated that addition of GDC enhanced the stability of the BCY phase in CO
2.
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Yasuhiro NOBUTA, Yoshihiro TAKAHASHI, Takamichi MIYAZAKI, Nobuaki TERA ...
2017 Volume 125 Issue 4 Pages
343-347
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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We prepared a borosilicate glass, in which the ZrO
2 phase is singly crystallizable, i.e., 15Na
2O–15ZrO
2–30B
2O
3–40SiO
2 glass, and investigated the texture and morphology of the resulting glass-ceramics. ZrO
2 dendrites with a tetragonal system (high-temperature phase) were developed as initial phase, and the tetragonal phase was transformed to the monoclinic phase (low-temperature phase) by elongation of the heat-treatment time, and finally the needle-/rod-like crystals on a scale of few hundred nanometers were obtained. The glass-ceramics with monoclinic ZrO
2 showed photoluminescence around 480 nm by excitation in the ultraviolet region. The effect of TiO
2-addition on the photoluminescent property was also considered.
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Naoto TEZUKA, Yuta OKAWA, Koichi KAJIHARA, Kiyoshi KANAMURA
2017 Volume 125 Issue 4 Pages
348-352
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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Nearly single-phase and almost fully-crystallized glass-ceramics of lithium chloroboracite Li
4+xB
7O
12+x/2Cl (
x = 0–1) were prepared by crystallization of precursor glasses derived from the Li
2O–B
2O
3–LiCl ternary system. The crystal structure of Li
4B
7O
12Cl (
x = 0) was refined by the Rietveld method in the space group
F43
c (no. 219). The precursor glass partially crystallized into Li
2B
4O
7 at ∼500°C and was subsequently converted to Li
4B
7O
12Cl at ∼600°C. The decomposition of Li
4B
7O
12Cl started at ∼700°C. The conductivity of Li
4B
7O
12Cl was much higher than that of Li
5B
7O
12.5Cl (
x = 1). The glass-ceramic sample with the highest weight fraction of Li
4B
7O
12Cl (∼0.98 of crystalline part with a degree of crystallinity of ∼0.96) exhibited a conductivity of ∼4.6 × 10
−4 S cm
−1 at 200°C and an activation energy of conductivity of ∼0.52 eV.
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Ayami SUZUKI, Yuya OAKI, Hiroaki IMAI
2017 Volume 125 Issue 4 Pages
353-356
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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Clay-based nanosheets were produced from montmorillonite modified with organic cations. Exfoliation of the clay was achieved by ion exchange with imidazolium and ammonium cations having long-chain alkyl groups. Dispersible nanosheets as a monolayer clay was obtained through the exfoliation by adjusting of the alkyl-chain length. Homogeneous dispersion of the nanosheets was demonstrated in a non-protonic polar liquid and polymeric solid media.
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Byung-Nam KIM, Tohru S. SUZUKI, Koji MORITA, Hidehiro YOSHIDA, Ji-Guan ...
2017 Volume 125 Issue 4 Pages
357-363
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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The densification behavior during the isothermal sintering of 7.8 mol % Y
2O
3-stabilized zirconia was examined in the intermediate and final stages of sintering. In the intermediate stage, it is shown that the relationship between the grain size and the relative density is not invariant, but is temperature dependent. The relationship is combined with the measured densification rate to evaluate the grain size exponent, the activation energy and an unspecified function of density. The evaluation of the characteristic parameters indicates that the densification and the grain growth are related to a mechanism of grain-boundary diffusion and sliding. The densification rate predicted with the evaluated parameters shows a good consistence to the measured rate. In the final stage, the densification rate is inversely proportional to the grain size, and the kinetics is well explained by using the diffusive model modified with a gas pressure in closed pores.
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Hiroki BANNO, Satoshi ICHIKAWA, Seiya TAKEDA, Toru ASAKA, Maggy COLAS, ...
2017 Volume 125 Issue 4 Pages
364-370
Published: April 01, 2017
Released on J-STAGE: April 03, 2017
JOURNAL
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Supplementary material
We investigated the crystal structures of high- and low-temperature phases in Sr
4[Al
6O
12]SO
4, and their thermal behavior by high-temperature X-ray powder diffraction (Cu
Kα
1), differential thermal analysis, and temperature-dependent Raman spectroscopy. The crystal structure at 298 K was isomorphous with that of Ca
4[Al
6O
12]SO
4 (space group
Pcc2 and
Z = 4). The structural model at 573 K (space group
I23 and
Z = 2) was characterized by the positional disordering of oxygen atoms that form [SO
4] tetrahedra. The maximum-entropy method-based pattern fitting method was used to confirm the validity of these structural models, in which conventional structure bias caused by assuming intensity partitioning was minimized. The starting temperature of the cubic-to-orthorhombic transformation during cooling (= 524 K) was slightly higher than that of the reverse transformation during heating (= 519 K). The negative thermal hysteresis (= −5 K) strongly suggested the transformation being thermoelastic. At around the transformation temperature during heating, the vibrational spectra, corresponding to the Raman-active [SO
4] internal stretching mode, showed the continuous and gradual change in the slope of full width at half maximum versus temperature curve. This strongly suggests that the phase transformation would be principally accompanied by the statistical disordering of oxygen-atom positions, without distinct dynamical reorientation of the [SO
4] tetrahedra.
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