/npsi/ctrl?action=rtdoc&an=9064983&lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=9064983&lang=frAccess and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1016/j.ssi. 2006.05.005 Solid State Ionics, 177, 13-14, pp. 1205Ionics, 177, 13-14, pp. -1210Ionics, 177, 13-14, pp. , 2006 A comparative study of the Ruddlesden-Popper series, Lan+1NinO3n+1 (n=1, 2 and 3), for solid-oxide fuel-cell cathode applications Amow, Gisele; Davidson, Isobel; Skinner, S. J.A comparative study of the Ruddlesden-Popper series, La n+1 Ni n O 3n+1 (n = 1, 2 and 3), for solid-oxide fuel-cell cathode applications AbstractA comparative investigation of the much-studied La 2 NiO 4+δ (n = 1) phase and the higher-order Ruddlesden-Popper phases, La n+1 Ni n O 3n+1 (n = 2 and 3), has been undertaken to determine their suitability as cathodes for intermediate-temperature solid-oxide fuel cells. As n is increased, a structural phase transition is observed from tetragonal I4/mmm in the hyperstoichiometric La 2 NiO 4.15 (n = 1) to orthorhombic Fmmm in the oxygen-deficient phases, La 3 Ni 2 O 6.95 (n = 2) and La 4 Ni 3 O 9.78 (n = 3). High temperature d.c. electrical conductivity measurements reveal a dramatic increase in overall values from n = 1, 2 to 3 with metallic behavior observed for La 4

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The solid-solution system Lai-*Ti03 was investigated over the range 0 < x < 0.33, i.e., involving end members LaTi03 and La2/3Ti03. X-ray single-crystal and powder neutron diffraction studies have established the structure of LamTiOs for the first time which is described in Pban with a -5.461(1) Á, b -5.482(1) Á, c = 7.759(3) Á. La vacancies are ordered largely in the z -V2 plane and Ti atoms are displaced from the centers of Ti-0 octahedra toward this plane giving rise to c-axis chains consisting of two short Ti-O bonds (1.906 Á) alternating with two long Ti-0 bonds (1.975 Á). The Pban structure is found for 0.25 < x < 0.33, an Ibmm structure for 0.20 < x < 0.25 and the Pbnm (GdFe03 type) structure for 0 < x < 0.20. The compounds La2/3Ti03 (x = 0.33) and Lao.?oTi03 Or = 0.30) are insulators, Lao.vsTiOs (x = 0.25) undergoes a metal-insulator transition and Lao.soTi03 (x = 0.20) to La0.92TiO3 (x -0.08) are metallic. Electrical, magnetic and structural properties are compared with those of the closely related Lai-*Sr*Ti03 and SrTi03-* systems. It is also argued that oxidized forms of LaTi03, described previously as LaTiOs-*, are better understood as Lai-*Ti03.