著者

下野 功 高橋 志郎 清水 健志 高村 巧 小林 淳哉 都木 靖彰

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.117, no.Supplement, pp.S5-S10, 2009 (Released:2009-04-01)

参考文献数

7

被引用文献数

3 3

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In this study of the phosphor utilizing a scallop shell, it was researched that the luminescence center was estimated from the chemical composition of the shell for the final purpose of the improvement of the luminescence property. The luminescence centers were estimated to be Cu and Mn from the experiment result and literature investigation. Furthermore, these concentrations were small by more than two orders in comparison with the commercially available phosphors. Therefore, improvement of the luminescence property can be expected by doping Cu and Mn to the shell and to investigate the relationship between these concentrations and the luminescence property to find the optimum concentration.

著者

Anupam PURWAR Ragini MUKHERJEE Krishnamurthy RAVIKUMAR S. ARIHARAN Nagarajan Kirupakaran GOPINATH Bikramjit BASU

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.124, no.4, pp.393-402, 2016-04-01 (Released:2016-04-01)

参考文献数

51

被引用文献数

39

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Zirconium diboride based ceramics, owing to their superior high temperature properties are potential materials for use as leading edge components in hypersonic space vehicles. However, the difficulty in sintering these ultra high temperature ceramics limit their applications to some extent. Sintering of such materials is usually accomplished by resorting to advanced sintering techniques such as Spark Plasma Sintering (SPS) accompanied by sinter aids to improve the sinterability. In this backdrop, the current work investigates the effect of Ti addition on the mechanical properties and sinterability of ZrB2–based ceramic composites. Tailored addition of Ti to ZrB2–18 wt. % SiC baseline composites not only improves the densification but also increases hardness and indentation toughness, when sintered using Multi Stage Spark Plasma Sintering technique. Microstructure and X-ray diffraction analysis reveals the presence of ultrafine grains of ZrB2 and SiC, which is found to be effective in obtaining a good hardness (up to 29 GPa) and reliable indentation toughness (up to 9 MPa·m1/2).

著者

Michele Back Jian Xu Jumpei Ueda Setsuhisa Tanabe

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.4, pp.57-61, 2023-04-01 (Released:2023-04-01)

参考文献数

26

被引用文献数

3

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Nd3+-doped Y3Al2Ga3O12 garnet ceramic pellet was prepared by solid state reaction and used as prototype to investigate the potential of Nd3+-activated garnet phosphors as Boltzmann thermometers for cryogenic and high temperature ranges. Despite the conventional use of the near-infrared emitting Nd3+-activated phosphors for biological applications, their real use is hindered by a low sensitivity in the physiological temperature range. Instead, the photoluminescence analysis in the 100–800 K range demonstrated interesting performances in both the cryogenic and high temperature ranges. Indeed, by taking advantage of the Stark levels of 4F3/2 (Z-levels) and the ratio between the emission from the 4F5/2 and the 4F3/2 excited states is possible to build two reliable Boltzmann thermometers in the same material working in the cryogenic temperature range (100–220 K) and at high temperatures (300–800 K), respectively.

著者

Hiroki ITO Akira MIURA Yosuke GOTO Yoshikazu MIZUGUCHI Chikako MORIYOSHI Yoshihiro KUROIWA Nataly Carolina ROSERO-NAVARRO Kiyoharu TADANAGA

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.129, no.5, pp.249-253, 2021-05-01 (Released:2021-05-01)

参考文献数

38

被引用文献数

1

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The magnetic and electronic properties of CeOInS2 and their influence on phase transition were analyzed in this study. High-temperature XRD measurements of CeOInS2 revealed that orthorhombic CeOInS2 transformed into tetragonal CeOInS2 at a high temperature of 636 K. The transport properties of CeOInS2 showed semiconducting behavior, with a larger temperature dependence of electronic resistivity in the tetragonal phase compared to that in the orthorhombic phase. Unlike structurally similar Ce(O,F)BiS2 superconductors that show long-range magnetic ordering, CeOInS2 neither exhibited superconductive transition nor long-range magnetic ordering at temperatures between 2 and 300 K.

著者

Takuma Noda Hanseul Kim Kenta Watanabe Kota Suzuki Naoki Matsui Ryoji Kanno Masaaki Hirayama

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.651-658, 2023-10-01 (Released:2023-10-01)

参考文献数

27

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The reaction distribution in the composite cathode of an all-solid-state battery (ASSB) was directly tracked by in situ scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX). Contact between an electrode active material and a solid electrolyte is important for improving the properties of ASSBs as a promising next-generation battery. An in situ analysis is significant for establishing strategies to obtain sufficient contact areas between the active material and solid electrolyte particles. SEM-EDX has the advantages of in-situ measurement in spatial/time resolution, non-destruction, and versatility. We investigated the sensitivity of EDX to the Na signal and distinguishable distance to ensure sufficient spatial/time resolution. The acceleration voltage of 5 kV for the electron beam provided the highest sensitivity to the Na signal among all acceleration voltages. The distinguishable distance decreased with increasing magnification owing to the decrease in pixel size. Cross-sectional SEM-EDX images of the TiS2–Na3PS4/Na3PS4/Na–Sn cell were collected during charge/discharge. The time variation of Na signal intensity confirms the deintercalation of Na+ in the TiS2–Na3PS4 cathode layer. Moreover, intercalation on the solid electrolyte side proceeded faster than that on the current collector side. This was because the rate-determining step was ionic conductivity rather than electronic conductivity based on the difference between ionic and electronic conductivities. Ex situ observations detected only a uniform distribution in the composite after Na+ diffusion had relaxed. Operando SEM-EDX is a new tool to directly explore the intermediate conditions of electrode materials under ASSB operation.

著者

Hiroki Matsuo

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.8, pp.429-436, 2023-08-01 (Released:2023-08-01)

参考文献数

115

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Ferroelectric materials exhibit a unique photovoltaic (PV) response that conventional pn junctions of semiconductors do not show. Above bandgap photovoltages, light-polarization-dependent photocurrents, photocurrent generation by terahertz light, etc. in ferroelectric PV effect are attractive features for novel optoelectronic devices. Recent studies on the ferroelectric PV effects have revealed that ferroelastic domain walls (DWs) are an active center for the generation of photocarriers. In this review paper, firstly, the history and status of studies on the DW-PV effect are briefly surveyed. Then, an analysis method that we have developed to experimentally quantify the magnitude of the PV response in the DW regions is introduced for BiFeO3-based ferroelectric epitaxial thin films. Moreover, materials design strategies for further enhancement of the photoresponse based on the engineering of impurity levels, domain structures, and their combinations are presented.

著者

Tatsumi ISHIHARA

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.122, no.1423, pp.179-186, 2014-03-01 (Released:2014-03-01)

参考文献数

26

被引用文献数

2 18

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Oxide ion conductivity in defect perovskite, mainly Pr2NiO4 with K2NiF4 structure, was studied in details. Defect perovskite oxide consists of perovskite block connected series to oxygen deficient block and although it is known that oxygen deficient block traps mobile oxide ion in lattice, interstitial oxygen introduced at rock salt block in Pr2NiO4 shows high mobility resulting in the high oxide ion conductivity. Oxide ion conductivity is much increased by doping Cu and Ga for Ni site and Pr deficient. The observed oxide ion conductivity was high like log (σ/Scm−1) = −0.25 at 1173 K. Conducting property of Pr1.91Ni0.75Cu0.21Ga0.05O4(PNCG)/Ce0.8Sm0.2O2(SDC) nano laminated film was further studied and the conductivity was much increased by formation of residual strain and the ion blocking method shows the transport number of the laminated film is almost unity and so high conductivity of PNCG/SDC laminated film could be assigned to pure oxide ion. Application of PNCG for anode of SOFC was further studied and it was found that surface activity of Pr2NiO4 doped with Cu and Ni shows high and so superior cathodic property was achieved at low temperature by mixing Pr2NiO4 with SDC. The maximum power density of the cell using LaGaO3 thin film electrolyte was achieved at 0.12 W/cm2 at 673 K.

著者

Wataru UNO Kotaro FUJII Eiki NIWA Shuki TORII Ping MIAO Takashi KAMIYAMA Masatomo YASHIMA

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.126, no.5, pp.341-345, 2018-05-01 (Released:2018-05-01)

参考文献数

46

被引用文献数

24

---

Crystal structure and neutron scattering length density distribution of a pyrochlore-type ytterbium titanate Yb2Ti2O7 have been investigated by in situ neutron powder diffraction measurements at 293 and 1173 K, Rietveld analysis and maximum-entropy method (MEM). In the MEM neutron scattering length density distributions of Yb2Ti2O7, the oxide ion O48f bonding to Ti cation was relatively localized at lower temperature of 293 K, while it was largely distributed at a higher temperature of 1173 K. At 1173 K, one oxide-ion diffusion path along the 〈110〉 unshared edge of TiO6 octahedron was clearly visualized and the other oxide-ion diffusion path along 〈100〉, strictly 〈2 −8x(O48f) + 3 8x(O48f) − 3〉, shared edge of TiO6 octahedron was also indicated. Here x(O48f) is the atomic coordinate x of O48f anion. The MEM neutron scattering length density distribution and difference bond valence sum map at 1173 K strongly suggested that the energy barrier for oxide-ion migration along 〈110〉 directions was lower than that along the 〈100〉 one. Oxide ions three-dimensionally diffuse through both the 〈110〉 and 〈100〉 paths across the unit cell.

著者

Shunsuke MURAI Tomohiko MATOBA Christopher T. NELSON Takuya KOMINE Koji FUJITA Xiaoqing PAN Katsuhisa TANAKA

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.121, no.1416, pp.710-713, 2013-08-01 (Released:2013-08-01)

参考文献数

21

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We have prepared composites with anisotropic microstructure consisting of silver nanoparticles and zinc oxide pillars using an oblique angle deposition technique, and examined the optical response originating from their anisotropic morphology. The sample was obtained in three steps. First, the assembly of silver nanoparticles was prepared on a silica glass substrate by electron-beam deposition of the silver thin film and subsequent heat treatment. Next, zinc oxide was obliquely grown by using a pulsed laser deposition. Finally the zinc oxide was crystallized by the post annealing to make an array of inclined pillars grown on the top of the silver nanoparticles. The structure and morphology of the composites were elucidated by a combination of X-ray diffraction analysis and transmission electron microscopy. Optical rotation spectroscopy clarifies that the composite shows optical birefringence due to its inclined pillar morphology. The optical rotation spectrum exhibits two peaks, one being associated to the localized surface plasmon resonance of the silver nanoparticles and the other the excitons in the zinc oxide pillars. The present fabrication method is simple and can be applied to obtain anisotropic composites with relatively large dimensions.

著者

Hiroyuki SHIMADA Toshiaki YAMAGUCHI Hirofumi SUMI Yuki YAMAGUCHI Katsuhiro NOMURA

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.125, no.4, pp.257-261, 2017-04-01 (Released:2017-04-03)

参考文献数

28

被引用文献数

9 10

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Perovskite-type mixed protonic and oxide ionic conductors for electrolyte material of solid oxide fuel cells were investigated, focusing on BaZr0.1Ce0.7Y0.1Yb0.1O3−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.

著者

Tomohiro ISHIYAMA Haruo KISHIMOTO Katherine DEVELOS-BAGARINAO Katsuhiko YAMAJI Toshiaki YAMAGUCHI Yoshinobu FUJISHIRO

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.125, no.4, pp.247-251, 2017-04-01 (Released:2017-04-03)

参考文献数

23

被引用文献数

9 10

---

The perovskite-type proton conductor with the composition of BaZr0.1Ce0.7Y0.1Yb0.1O3−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 CO2 or CO2 + H2 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)Ybx)2NiO5. Moreover, different decomposition reactions depending on the atmosphere have been inferred. In a pure CO2 atmosphere, barium carbonate formation occurred without appearance of the CeO2-based phase, in other words, without decomposition of the perovskite phase. On the other hand, in hydrogen-containing CO2 atmosphere, both the barium carbonate and CeO2-based phase were observed.

著者

Takuya Kataoka Yuhi Yasuhira Eiji Fujii Tomohiko Yoshioka Satoshi Hayakawa

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.9, pp.569-574, 2023-09-01 (Released:2023-09-01)

参考文献数

29

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In this study, the impact of chitosan (CS) on Mg2+ incorporation into hydroxyapatite (HAp) was investigated. Initial Mg/(Ca+Mg) ratios of 0–0.15 resulted in Mg-incorporated HAp containing CS (CMgHAp), while a ratio of 0.2 yielded amorphous calcium phosphate containing CS. Mg/(Ca+Mg) and (Ca+Mg)/P molar ratios of the obtained CMgHAp particles were lower than those of Mg-incorporated HAp particles without CS, suggesting that Mg incorporation into HAp was suppressed by CS. Initial Mg/(Ca+Mg) ratio of 0.025 led to CMgHAp particles with lower specific surface area than HAp particles containing CS, while ratios of 0.05–0.15 led to particles with higher specific surface area. Transmission electron microscopy showed aggregated particles of CMgHAp, since the observed particle sizes were larger than the crystallite sizes of CMgHAp calculated using X-ray diffraction patterns. Analyses of Fourier transform infrared spectroscopy confirms the interaction of CS with the phosphate group in Mg-incorporated HAp. Calcination of the CMgHAp particles decreased the particle size and increased the specific surface area due to decomposition of CS, indicating that CS aggregated Mg-incorporated HAp particles.

著者

Naoki Tarutani Miki Asanome Kenji Okada Masahide Takahashi Takuo Minato Masahiro Sadakane Kiyofumi Katagiri Kei Inumaru

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.830-836, 2023-10-01 (Released:2023-10-01)

参考文献数

44

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Additive manufacturing by vat-photopolymerization is important technique to prepare designed objects because of its features of availability, low cost, low energy consumption, and high-speed printing. One of the major challenges of this technique is how to expand the chemical composition towards metals and ceramics in addition to organic compounds. In this paper, we report synthesis of highly concentrated nanocolloids of nickel hydroxide acrylate and use them for vat-photopolymerization. Epoxide-mediated basification induced formation of dispersed nickel hydroxide acrylate monolayer/bilayer nanoparticles (diameter of 2.31 nm). The concentration of nanocolloid was prepared as 2.5 mol L−1 (Ni basis), which corresponds to 43 wt % and 30 vol %. The concentrated nanocolloids enabled to produce objects through vat-photopolymerization by using commercially available 3D printers. Addition of small quantity of organic cross-linker efficiently interconnect nanoparticles to form bulky objects. Owing to the organic moiety of nickel hydroxide salt nanoparticles, metal/carbon composites formed by heat-treatment without any reduction gas supply. Further heat-treatment led metal oxide bulky object with macroporous structure.

著者

Yuichi Shimakawa

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.771-776, 2023-10-01 (Released:2023-10-01)

参考文献数

51

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Oxides containing unusually high-valence transition-metal ions often exhibit charge transitions to relieve the electronic instabilities. A-site-ordered quadruple perovskites LnCu3Fe4O12 with the unusually high-valence Fe3.75+, which are synthesized under high-pressure conditions, show intermetallic-charge-transfer transitions. In this review article, novel thermo-related functional properties induced by the charge transitions in LnCu3Fe4O12 are highlighted. A large negative-thermal-expansion behavior was observed at the intermetallic-charge-transfer transition temperature. The negative-thermal-expansion property is primarily caused by the size effect of constituent ions by the charge changes. The property is useful for developing materials to compensate the normal positive thermal expansion. Significant latent heat was also found to be provided by the intermetallic-charge-transfer transition in LnCu3Fe4O12. The large latent heat is considered to be related with unusual first-order magnetic entropy change induced by the charge transition. The large entropy change can be utilized for thermal control through a caloric effect, which can make effective energy systems for thermal energy storage and refrigeration.

著者

Daisuke Mori Miho Sato Sou Taminato Nobuyuki Imanishi Kota Suzuki Masaaki Hirayama

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.690-695, 2023-10-01 (Released:2023-10-01)

参考文献数

36

被引用文献数

1

---

Li ionic conductors that are stable to lithium metal with high ionic conductivity are required as solid electrolytes for all-solid-state lithium metal batteries with high energy density. Lithium dendrite growth leading to short-circuit is one of the major issues to solve for developing practical batteries using lithium metal electrodes. We have introduced Li3PO4 (LPO) and Li3BO3 (LBO) as a grain boundary phase in the garnet-type lithium ionic conductor, Li6.25Ga0.25La3Zr2O12 (LGLZ), by co-sintering. The lattice parameters, sinterability, elemental distribution, particle morphology, and electrochemical properties have been investigated. The sinterability has decreased with the introduction of LPO and LBO, while no significant change in the ionic conductivity is observed. The LGLZ with LPO was unstable to Li metal and did not exhibit the improvement of Li plating/stripping. Meanwhile, the LBO introduction into the grain boundary as a functional core increased the critical current density of the short circuit. Li dendrite growth could be suppressed by modifying the grain boundaries of the sintered body.

著者

Kota Suzuki Jinan Cui Jiang Peilu Hanseul Kim Yumi Yamaguchi Satoshi Hori Masaaki Hirayama Ryoji Kanno

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.717-722, 2023-10-01 (Released:2023-10-01)

参考文献数

20

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In this study, high-sulfur-containing carbon replica (sulfur-rich S-CR) composites were prepared using a melt-diffusion method. Melt diffusion under vacuum enabled the introduction of four times the weight ratio of sulfur into the mesopores of a carbon replica (CR). The obtained sulfur-rich S-CR exhibited an initial discharge capacity of 700 mAh gsulfur−1, indicating the low utilization of sulfur in the composite. The classification of the particle sizes of the solid electrolyte and CR contributed to the improvement in electrochemical performance. An initial discharge capacity of over 1,200 mAh g−1 was confirmed for the S-CR composite using the smaller solid electrolyte and CR prepared via a dry classification process. An analysis of the effect of the additives indicated that the rational design of electronic and ionic conduction pathways is required for higher cycle performance when using sulfur-rich S-CRs.

著者

Takumi Yabuzaki Miho Sato Hanseul Kim Kenta Watanabe Naoki Matsui Kota Suzuki Satoshi Hori Kazuhiro Hikima Satoshi Obokata Hiroyuki Muto Atsunori Matsuda Ryoji Kanno Masaaki Hirayama

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.131, no.10, pp.675-684, 2023-10-01 (Released:2023-10-01)

参考文献数

36

被引用文献数

1

---

Sulfide-type solid electrolytes for all-solid-state lithium-ion batteries are required to have high ionic conductivity, high (electro) chemical stability, and suitable mechanical properties. Compositing different materials is widely performed in developing multifunctional materials. However, only a few studies have investigated sulfide electrolytes due to the concern of lowering ionic conductivity. In this study, composite electrolytes comprising Li10GeP2S12 (LGPS)-type electrolytes and nanosized Al2O3 are fabricated by a solid-state reaction. Al2O3 particles are mainly located in the voids between LGPS particles, whereas very limited oxygen content is substituted for sulfur in the LGPS structure. LGPS–Al2O3 composites exhibit ionic conductivities of ∼5 mS cm−1 without significant changes by compositing Al2O3. LGPS–Al2O3 composites are softer and have higher atmospheric stability than uncomposed LGPS. All solid-state cells that use air-exposed LGPS–Al2O3 as a separator layer exhibit an improved cycle retention compared with that using air-exposed LGPS. These results demonstrate that electrolyte compositing is an effective means of improving other properties while maintaining high lithium ionic conductivity.

著者

Karina Maria PACIEJEWSKA Yi YU Sascha KÜHN Andreas WEBER Matthias KLEBER

出版者

公益社団法人 日本セラミックス協会

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.123, no.1436, pp.171-177, 2015-04-01 (Released:2015-04-01)

参考文献数

15

被引用文献数

6 7

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The development of a dense chemical reaction blocking layer (CRBL) for micro-tubular solid oxide fuel cells (SOFC) was the aim of this study. The electrochemical performance and stability of SOFCs were also investigated since they strongly depend on fabrication conditions for the electrolyte and CRBL layers. Slurries of two commercial Ce0.8Gd0.2O1.90 powders were prepared and deposited by dip coating onto micro-tubular SOFCs. The results indicate that the layer density and homogeneity are essentially determined by the width of particle size distribution (PSD) apart from the colloidal stability. Two methods were applied for achieving a narrow PSD additional to dispersion: grinding and centrifugation. Particles with a very narrow PSD obtained through centrifugation process could be sintered together even at 1300°C and a layer with a density close to 99% could be reached. In contrast, simple ultrasonic dispersion of powders diminished the distribution width insufficiently and gave porous layer. Impedance measurements showed clear relationship between GDC layer density and ohmic resistance of the cells which directly correlates to their performance with a power density 0.75 W/cm2 at 0.7 volt and OCV~1.06 V obtained at 850°C for the cells with the densest GDC layer.

著者

Takeshi HAGIWARA Katsuhiro NOMURA Hiroyuki KAGEYAMA

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.125, no.2, pp.65-70, 2017-02-01 (Released:2017-02-01)

参考文献数

20

被引用文献数

10 15

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We synthesized Eu2Zr2O7 and La2Zr2O7 using high purity ZrO2 of extremely low Hf content. The crystal structures of Eu2Zr2O7 and La2Zr2O7 were refined by the Rietveld analysis of the powder X-ray diffraction data (indexed as a cubic pyrochlore-type structure, space group: No.227, Fd3m) measured from 1173 to 298 K in a dry condition and from 1173 to 323 K in a wet condition. The crystal structure of La2Zr2O7 is near to an ideal pyrochlore-type structure, whereas that of Eu2Zr2O7 is a distorted pyrochlore-type structure. The thermal expansion coefficients of Eu2Zr2O7 were larger than those of La2Zr2O7. The value of the equivalent isotropic atomic displacement parameters (Beq) calculated from the anisotropic atomic displacement parameter for the Zr in Eu2Zr2O7 at 298 K was around 1.4 Å2, and the increase of this value in Eu2Zr2O7 with increasing temperature was smaller than that in La2Zr2O7.

著者

Takeshi HAGIWARA Hiroshi YAMAMURA Katsuhiro NOMURA Manabu IGAWA

出版者

The Ceramic Society of Japan

雑誌

Journal of the Ceramic Society of Japan (ISSN:18820743)

巻号頁・発行日

vol.121, no.1410, pp.205-210, 2013-02-01 (Released:2013-02-01)

参考文献数

29

被引用文献数

20 22

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Crystal structures of the Ln2Zr2O7 (Ln = Nd and La) were refined by the Rietveld analysis of powder neutron diffraction (ND) data at room temperature. La2Zr2O7 had a pyrochlore (P)-type structure of almost completely ordered for oxygen vacancy. On the other hand, Nd2Zr2O7 had the P-type structure for the oxygen vacancy distributed between the O2 (8b) and O3 (48f) sites. The Rietveld refinement results of powder X-ray diffraction (XRD) data of Ln2Zr2O7 (Ln = Eu, Nd and La) indicated that the Ln3+ and Zr4+ ions exist in ordered states in 16c and 16d sites, respectively. The refined lattice parameters (a), occupancies (g) for oxygen sites (O1, O2 and O3) and x-positional parameters for O3 (48f) site of La2Zr2O7 and Nd2Zr2O7 by using powder XRD data were in almost agreement with those by using powder ND data. The refined ND and XRD data of Ln2Zr2O7 (Ln = Eu, Nd and La) system revealed that the O3 (48f) site occupancy (g48f) decreases with increasing O2 (8b) site occupancy, while O1 (8a) site occupancy keeping 1.0. The change in oxide-ion conductivity (σ) in Ln2Zr2O7 (Ln = Eu, Nd and La) system can be related to a change in the product of site occupancy (g48f) and the oxygen vacancy rate (1-g48f) in the O3 (48f) site, g48f(1-g48f).