LaGaO3系電解質の湿式法による薄膜化と可逆動作固体酸化物セルに関する研究

主1材料物性工

LaGaO3系電解質の湿式法による薄膜化と可逆動作固体酸化物セルに関する研究

主1材料物性工

Ruddlesden Popper oxides of LnSr(3)Fe(3)O(10-delta) (Ln = La, Pr, Nd, Sm, Eu, and Gd) as active cathodes for low temperature solid oxide fuel cells

Ruddlesden Popper type oxides of LnSr(3)Fe(3)O(10-delta) (Ln - La, Pr, Nd, Sm, Eu, and Gd) have been investigated as active cathodes for solid oxide fuel cells (SOFCs). Among the examined LnSr(3)Fe(3)O(10-delta), it was found that PrSr3Fe3O10-delta shows the highest activity for the cathode reaction. The prepared LnSr(3)Fe(3)O(10-delta) oxides have a tetragonal crystal structure with the space group I4/mmm. With decreasing the ionic size of Ln(3+), the unit cell volume and crystallite size decrease. The temperature and P-O2 dependences of electrical conductivities indicate the metal-like behaviour and the predominant hole conduction. The thermal expansion coefficient (TEC) values derived from the non-linear expansion curves of LnSr(3)Fe(3)O(10-delta) are reasonably compatible with those of La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte. The catalytic activity as cathodes for H-2-SOFCs depended on Ln ions. A high cathodic activity was achieved on LnSr(3)Fe(3)O(10-delta) (PSFO10) and a maximum power density of 0.51 W cm(-2) was achieved at 1073 K when 0.3 mm thick LSGM electrolyte was used. The surface exchange coefficient, k, also confirms the high activity for the dissociation of oxygen on PSFO10. Therefore, PrSr3Fe3O10-delta is highly promising as a cathode for low temperature SOFCsclose0

(61)Ni synchrotron radiation-based Mössbauer spectroscopy of nickel-based nanoparticles with hexagonal structure.

ニッケルナノ粒子の放射光メスバウアー吸収分光測定に成功 --先端ナノ材料の機能発現メカニズムの解明に期待--. 京都大学プレスリリース. 2016-02-18.We measured the synchrotron-radiation (SR)-based Mössbauer spectra of Ni-based nanoparticles with a hexagonal structure that were synthesised by chemical reduction. To obtain Mössbauer spectra of the nanoparticles without (61)Ni enrichment, we developed a measurement system for (61)Ni SR-based Mössbauer absorption spectroscopy without X-ray windows between the (61)Ni84V16 standard energy alloy and detector. The counting rate of the (61)Ni nuclear resonant scattering in the system was enhanced by the detection of internal conversion electrons and the close proximity between the energy standard and the detector. The spectrum measured at 4 K revealed the internal magnetic field of the nanoparticles was 3.4 ± 0.9 T, corresponding to a Ni atomic magnetic moment of 0.3 Bohr magneton. This differs from the value of Ni3C and the theoretically predicted value of hexagonal-close-packed (hcp)-Ni and suggested the nanoparticle possessed intermediate carbon content between hcp-Ni and Ni3C of approximately 10 atomic % of Ni. The improved (61)Ni Mössbauer absorption measurement system is also applicable to various Ni materials without (61)Ni enrichment, such as Ni hydride nanoparticles

Nematic quantum critical point without magnetism in FeSe1−xSx superconductors

In most unconventional superconductors, the importance of antifer- romagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for elec- tron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing us to identify the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or co- existing orders. Here we report systematic elastoresistance mea- surements in FeSe1−xSx superconductors, which, unlike other iron- based families, exhibit an electronic nematic order without accom- panying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x, whereas the nematic fluctuations are strongly enhanced. Near x 0.17, the nematic sus- ceptibility diverges towards absolute zero, revealing a nematic quan- tum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1−xSx as a unique nonmag- netic system suitable for studying the impact of nematicity on super- conductivity.UTokyo Research掲載「新しい種類の超伝導の発生源になりうるか？」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/discovery-may-point-to-new-source-of-superconductivity.htmlUTokyo Research "Discovery may point to new source of superconductivity" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/discovery-may-point-to-new-source-of-superconductivity.htm