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Journal Articles

Study of annealing effect on crystal and local structures of doped zirconia using multi probe

Ito, Takanori*; Mori, Masashi*; Inukai, Manabu*; Nitani, Hiroaki*; Yamamoto, Takashi*; Miyanaga, Takashi*; Igawa, Naoki; Kitamura, Naoto*; Ishida, Naoya*; Idemoto, Yasushi*

Photon Factory News, 33(1), p.18 - 24, 2015/05

The effect of the annealing on the crystal and local structures of doped zirconia was investigated by multi-probe technique using synchrotron X-ray and neutron diffraction, and first principles calculation. It was revealed that the annealing process enhances the periodic distortion of some zirconia compounds by Rietveld/ maximum entropy methods applied to the SR-X-ray and neutron diffractions. In addition, the combined X-ray absorption spectroscopy and first-principles calculations results showed the ZrO$$_{8}$$ polyhedra in zirconia were distorted by the annealing. Those results indicate that the degradation of oxide ionic conductivity by the annealing was related to the periodic distortion in zirconia.

Journal Articles

Effect of annealing on crystal and local structures of doped zirconia using experimental and computational methods

Ito, Takanori*; Mori, Masashi*; Inukai, Manabu*; Nitani, Hiroaki*; Yamamoto, Takashi*; Miyanaga, Takashi*; Igawa, Naoki; Kitamura, Naoto*; Ishida, Naoya*; Idemoto, Yasushi*

Journal of Physical Chemistry C, 119(16), p.8447 - 8458, 2015/04

 Times Cited Count:13 Percentile:48.36(Chemistry, Physical)

The effects of the annealing process on the crystal and local structures of the doped zirconia were investigated by Rietveld refinements of synchrotron X-ray and neutron diffraction, maximum entropy method (MEM), X-ray absorption spectroscopy (XAS) and first principles calculation (FPC). This study reveals that the crystal structures of the sintered and annealed ((Zr$$_{0.85}$$Y$$_{0.15}$$)O$$_{2}$$ and (Zr$$_{0.81}$$Sc$$_{0.18}$$Ce$$_{0.01}$$)O$$_{2}$$) are cubic with the space ${it Fm}$-3${it m}$ having large atomic displacement parameters (${it U}$). For the annealed (Zr$$_{0.85}$$Y$$_{0.15}$$)O$$_{2}$$, the ${it U}$ values reduce, and the electrons around the Zr/oxide ion sites gather at the center of each site. On the other hand, the annealed (Zr$$_{0.81}$$Sc$$_{0.18}$$Ce$$_{0.01}$$)O$$_{2}$$ shows the opposite tendency to that of the annealed (Zr$$_{0.85}$$Y$$_{0.15}$$)O$$_{2}$$.

Journal Articles

Protonic conduction, crystal and electronic structures of La$$_{0.9}$$Ba$$_{1.1}$$Ga$$_{0.95}$$Mg$$_{0.05}$$O$$_{4-delta}$$

Hamao, Naoki*; Kitamura, Naoto*; Ito, Takanori*; Igawa, Naoki; Idemoto, Yasushi*; Daido, Hiroyuki; Kaku, Masanori*; Kubodera, Masakazu*

Solid State Ionics, 253, p.123 - 129, 2013/12

 Times Cited Count:3 Percentile:17.78(Chemistry, Physical)

La$$_{0.9}$$Ba$$_{1.1}$$Ga$$_{0.95}$$Mg$$_{0.05}$$O$$_{4-delta}$$ which is one of the candidates for solid electrolyte of solid oxide fuel cell was synthesized by means of a conventional solid-state reaction, and investigated by conductivity measurements, the Rietveld and maximum entropy method analyses using neutron and synchrotron X-ray diffraction data. Conductivity measurements indicated that simultaneous Ba and Mg substitutions for LaBaGaO$$_{4}$$ were effective way to improve the protonic conductivity. From the Rietveld and maximum entropy method analyses, it was confirmed that La$$_{0.9}$$Ba$$_{1.1}$$Ga$$_{0.95}$$Mg$$_{0.05}$$O$$_{4-delta}$$ kept the same crystal structure as LaBaGaO$$_{4}$$ even at elevated temperature, i.e. 1000 K, and that protons existed around the O3 site and formed hydrogen bonds. It is also found that oxygens in LaBaGaO$$_{4}$$-based samples formed Ga-O$$_{4}$$ tetrahedra, and the bonding strength was varied by the partial substitutions.

Journal Articles

Study of oxygen ion diffusion in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33-delta}$$ through ${it in-situ}$ neutron diffractions at 300 and 720 K

Ito, Takanori*; Hirai, Takene*; Yamashita, Junichi*; Watanabe, Shoji*; Kawata, Etsuya*; Kitamura, Naoto*; Idemoto, Yasushi*; Igawa, Naoki

Physica B; Condensed Matter, 405(8), p.2091 - 2096, 2010/04

 Times Cited Count:13 Percentile:53.76(Physics, Condensed Matter)

We analyze the mechanism of oxygen ion diffusion in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33-delta}$$ by using the Rietveld refinement, the maximum entropy method (MEM) analysis, and MEM-based pattern fitting (MPF) with ${it in-situ}$ neutron diffractions at 300 and 720 K. We speculate that when $$U$$$$_{rm aniso}$$ and neutron scattering density of O1(4${it c}$) site with a large number of vacancies metamorphose into that with anisotropy directed toward the O1(4${it c}$) and O2(8${it d}$) sites at 720 K, the oxygen ions diffuse along the paths between O1(4${it c}$) and O1(4${it c}$), and O1(4${it c}$) and O2(8${it d}$).

Journal Articles

Relationship between average and local crystal structure and the ferroelectric properties of a Sr-Bi-Ta-Si-O ferroelectric material

Idemoto, Yasushi*; Taniyama, Satoshi*; Iikubo, Satoshi*; Shamoto, Shinichi; Richardson, J. W.*

Journal of Physics and Chemistry of Solids, 70(8), p.1156 - 1165, 2009/08

 Times Cited Count:3 Percentile:19.38(Chemistry, Multidisciplinary)

Journal Articles

Study of mechanism of mixed conduction due to electrons and oxygen ions in (La$$_{0.75}$$Sr$$_{0.25}$$)MnO$$_{3.00}$$ and (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$ through rietveld refinement and MEM analysis

Ito, Takanori*; Shirasaki, Saori*; Fujie, Yoshinori*; Kitamura, Naoto*; Idemoto, Yasushi*; Osaka, Keiichi*; Hirosawa, Ichiro*; Igawa, Naoki

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 77(2), p.161 - 168, 2009/02

 Times Cited Count:2 Percentile:6.13(Electrochemistry)

We analyzed the mechanism of mixed conduction due to electrons and oxygen ions in (La$$_{0.75}$$Sr$$_{0.25}$$)MnO$$_{3.00}$$ and (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$ through the Rietveld refinement and maximum entropy method analyses of neutron and synchrotron X-ray diffractions. It was found that Mn-O plane in (La$$_{0.75}$$Sr$$_{0.25}$$)MnO$$_{3.00}$$ has a strong, isotropic covalent bond that enables conduction of electrons. The (Co, Fe)-O2 plane with a covalent bond and a low concentration of oxygen vacancies in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$ can also conduct electrons. On the other hand, the (Ba, Sr)-O1 plane in (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$, which has a high concentration of oxygen vacancies, large isotropic displacement parameter, and a strong ionic bond, is responsible for the diffusion of oxygen ions.

Journal Articles

Determination of crystal structure and charge density of (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$ by Rietveld refinement and maximum entropy method analysis

Ito, Takanori*; Nishida, Yuki*; Tomita, Aya*; Fujie, Yoshinori*; Kitamura, Naoto*; Idemoto, Yasushi*; Osaka, Keiichi*; Hirosawa, Ichiro*; Igawa, Naoki

Solid State Communications, 149(1-2), p.41 - 44, 2009/01

 Times Cited Count:33 Percentile:77.94(Physics, Condensed Matter)

The crystal structure and charge density of (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{2.33}$$ were investigated by the Rietveld refinement method and the maximum entropy method by using neutron and synchrotron X-ray diffraction. The crystal structure was refined by using the split atom model to cation sites with the space group, ${it Pnma}$. The site occupancies of O1(4${it c}$) and O2(8${it d}$) sites were 0.59 and 0.87, respectively. It was found that the (Co, Fe)-O2 plane in the sample has anisotropic covalent and ionic bands, and that the (Ba, Sr)-O1 bond was ionic with a low charge density.

Oral presentation

Ferroelectric performance and average, local crystal structure of (Pb,Si)(Zr,Ti,Nb)O$$_3$$ ferrelectric material

Komiya, Shoko*; Idemoto, Yasushi*; Iikubo, Satoshi; Shamoto, Shinichi

no journal, , 

no abstracts in English

Oral presentation

Relationship between average, local crystal structure, and ferroelectric performances of Bi-Si-O added Sr-Ce-Bi-Ta-O ferroelectric material

Taniyama, Satoshi*; Idemoto, Yasushi*; Iikubo, Satoshi; Shamoto, Shinichi

no journal, , 

no abstracts in English

Oral presentation

Study of electron-oxide ion mixed conduction in SOFC cathode materials by MEM

Ito, Takanori*; Yokote, Takenori*; Kitamura, Naoto*; Idemoto, Yasushi*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki

no journal, , 

The investigation and development of the cathode materials are one of the major subjects to decrease the operation temperature for solid oxide fuel cell. In this study, we measured the neutron and synchrotron X-ray diffraction of La$$_{0.73}$$Sr$$_{0.24}$$MnO$$_{3}$$ and (Ba$$_{0.5}$$Sr$$_{0.5}$$)(Co$$_{0.8}$$Fe$$_{0.2}$$)O$$_{3-delta}$$. We discuss the mechanism of the electron-oxide ion mixed conduction from the Rietveld and the maximum entropy method analyses.

Oral presentation

Crystal structure of SOFC cathode materials by neutron and synchrotron X-ray diffraction

Ito, Takanori*; Yokote, Takenori*; Kitamura, Naoto*; Idemoto, Yasushi*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki

no journal, , 

Perovskite-type oxides with electron-oxide ion mixed conduction are attractive materials as a cathode for solid oxide fuel cell. Although (La,Sr)MnO$$_{3}$$ is applied for this purpose, (Ba,Sr)(Co,Fe)O$$_{3-delta}$$ has much attention because it has lower operation temperature. In this study, we carried out the neutron and synchrotron X-ray diffraction study on those materials, and discuss the difference in crystal structure including the nuclei and electron distribution on the transition metal-oxygen plain in the crystal from the results of the Rietveld and the maximum entropy method analyses.

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