Interstitial Oxygen in Perovskite-Related Sr6–2xNb2+2xO11+3x
详细信息 查看全文
- 作者：Man-Rong Li ; Seung-Tae Hong
- 刊名：Chemistry of Materials
- 出版年：2008
- 出版时间：April 22, 2008
- 年：2008
- 卷：20
- 期：8
- 页码：2736 - 2741
- 全文大小：1076K
- 年卷期：v.20,no.8(April 22, 2008)
- ISSN：1520-5002
文摘
Solid solutions of perovskite-related compounds Sr6–2xNb2+2xO11+3x(0.103 ≤ x ≤ 0.333) were synthesized at 1523 K in air. The crystal structures were determined and refined by a combined powder X-ray and neutron Rietveld method (Fm3̅m, a = 8.3103Å, Z = 2, Rp = 4.02%, wRp = 5.63%, χ2 = 4.44, 23 °C, for example, with x = 0.103). According to the Fourier synthesis map analysis, a new structural model, which includes interstitial oxygen, is proposed for the title compounds. The metal atoms fully occupy the A or B-sites of the perovskite (ABO3) structure. The pure Nb site and the mixed Sr/Nb site form a rock-salt type ordering in the B-site. The oxygen atoms and anionic vacancies are distributed statistically over the normal (O1 at 24e site) and interstitial positions (O2 at 48h site), and the occupancies for the interstitial sites are 8.5–15.4%. According to the electrical conductivities as functions of temperature and oxygen partial pressure under dry and wet air, the compounds are predominant oxide ion conductors at high temperatures and proton conductors as well at lower temperatures under wet air. The total conductivity increases with increasing strontium content, or decreasing oxygen content but increasing site occupancy at the interstitial oxygen site.