Framework 'interstitial' oxygen in La10(GeO4)5-(GeO5)O2 apatite electrolyte
Framework 'interstitial' oxygen in La10(GeO4)5-(GeO5)O2 apatite electrolyte
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DOI：
10.1107/s0108768107024317
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发表时间：
2007-08-01
期刊：
影响因子：
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通讯作者：
White, T. J.
中科院分区：
文献类型：
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作者：
Pramana, Stevin S.;Klooster, Wim T.;White, T. J.
磷灰石中低温下的氧传导使这些材料有可能用作固体氧化物燃料电池中的电解质，但我们对导致离子迁移的缺陷结构的理解并不完整。虽然沿[001]通道的传导占主导地位，但已认识到相当大的隧道间迁移率。使用化学计量“La-10(GeO4)(6)O-3”的中子粉末衍射表明，该化合物更正确地描述为 La-10(GeO4)(5)-GeO5) O-2 磷灰石，其中高浓度的间隙氧驻留在通道壁内。研究表明，这些骨架间隙 O 原子提供了一个离子库，可以通过隧道间氧扩散机制迁移到磷灰石的导电通道中，从而将 GeO4 四面体瞬时转化为 GeO5 扭曲的三角双锥体。这种结构改变与已知的晶体化学一致并且通常可以发生在氧化物磷灰石中。
Oxygen conduction at low temperatures in apatites make these materials potentially useful as electrolytes in solid-oxide fuel cells, but our understanding of the defect structures enabling ion migration is incomplete. While conduction along [001] channels is dominant, considerable inter- tunnel mobility has been recognized. Using neutron powder diffraction of stoichiometric 'La-10(GeO4)(6)O-3', it has been shown that this compound is more correctly described as an La-10(GeO4)(5)- GeO5) O-2 apatite, in which high concentrations of interstitial oxygen reside within the channel walls. It is suggested that these framework interstitial O atoms provide a reservoir of ions that can migrate into the conducting channels of apatite, via a mechanism of inter- tunnel oxygen diffusion that transiently converts GeO4 tetrahedra to GeO5 distorted trigonal bipyramids. This structural modification is consistent with known crystal chemistry and may occur generally in oxide apatites.