Structural origin of the anisotropic and isotropic thermal expansion of K2NiF4-type oxides

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dc.contributor.authorKawamura, Ken_AU
dc.contributor.authorYashima, Men_AU
dc.contributor.authorFujii, Ken_AU
dc.contributor.authorOmoto, Ken_AU
dc.contributor.authorHibino, Ken_AU
dc.contributor.authorYamada, Sen_AU
dc.contributor.authorHester, JRen_AU
dc.contributor.authorAvdeev, Men_AU
dc.contributor.authorMiao, Pen_AU
dc.contributor.authorTorii, Sen_AU
dc.contributor.authorKamiyama, Ten_AU
dc.date.accessioned2021-07-30T02:10:39Zen_AU
dc.date.available2021-07-30T02:10:39Zen_AU
dc.date.issued2015-04-02en_AU
dc.date.statistics2021-07-19en_AU
dc.description.abstractK2NiF4-type LaSrAlO4 and Sr2TiO4 exhibit anisotropic and isotropic thermal expansion, respectively; however, their structural origin is unknown. To address this unresolved issue, the crystal structure and thermal expansion of LaSrAlO4 and Sr2TiO4 have been investigated through high-temperature neutron and synchrotron X-ray powder diffraction experiments and ab initio electronic calculations. The thermal expansion coefficient (TEC) along the c-axis (αc) being higher than that along the a-axis (αa) of LaSrAlO4 [αc = 1.882(4)αa] is mainly ascribed to the TEC of the interatomic distance between Al and apical oxygen O2 α(Al–O2) being higher than that between Al and equatorial oxygen O1 α(Al–O1) [α(Al–O2) = 2.41(18)α(Al–O1)]. The higher α(Al–O2) is attributed to the Al–O2 bond being longer and weaker than the Al–O1 bond. Thus, the minimum electron density and bond valence of the Al–O2 bond are lower than those of the Al–O1 bond. For Sr2TiO4, the Ti–O2 interatomic distance, d(Ti–O2), is equal to that of Ti–O1, d(Ti–O1) [d(Ti–O2) = 1.0194(15)d(Ti–O1)], relative to LaSrAlO4 [d(Al–O2) = 1.0932(9)d(Al–O1)]. Therefore, the bond valence and minimum electron density of the Ti–O2 bond are nearly equal to those of the Ti–O1 bond, leading to isotropic thermal expansion of Sr2TiO4 than LaSrAlO4. These results indicate that the anisotropic thermal expansion of K2NiF4-type oxides, A2BO4, is strongly influenced by the anisotropy of B–O chemical bonds. The present study suggests that due to the higher ratio of interatomic distance d(B–O2)/d(B–O1) of A22.5+B3+O4 compared with A22+B4+O4, A22.5+B3+O4 compounds have higher α(B–O2), and A22+B4+O4 materials exhibit smaller α(B–O2), leading to the anisotropic thermal expansion of A22.5+B3+O4 and isotropic thermal expansion of A22+B4+O4. The “true” thermal expansion without the chemical expansion of A2BO4 is higher than that of ABO3 with a similar composition. © 2015 American Chemical Societyen_AU
dc.identifier.citationKawamura, K., Yashima, M., Fujii, K., Omoto, K., Hibino, K., Yamada, S., Hester, J. R., Avdeev, M., Miao, P., Torii, S., & Kamiyama, T. (2015). Structural origin of the anisotropic and isotropic thermal expansion of K2NiF4-type oxides. Inorganic Chemistry, 54(8), 3896–3904. doi:10.1021/acs.inorgchem.5b00102en_AU
dc.identifier.issn1520-510Xen_AU
dc.identifier.issue8en_AU
dc.identifier.journaltitleInorganic Chemistryen_AU
dc.identifier.pagination3896-3904en_AU
dc.identifier.urihttps://doi.org/10.1021/acs.inorgchem.5b00102en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/11167en_AU
dc.identifier.volume54en_AU
dc.language.isoenen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectThermal expansionen_AU
dc.subjectNeutron diffractionen_AU
dc.subjectOxygenen_AU
dc.subjectOxidesen_AU
dc.subjectGranular materialsen_AU
dc.subjectX-ray diffractionen_AU
dc.titleStructural origin of the anisotropic and isotropic thermal expansion of K2NiF4-type oxidesen_AU
dc.typeJournal Articleen_AU
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