| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 262.21 KB | Adobe PDF |
Orientador(es)
Resumo(s)
The synthesis and the structural characterization of tin niobates Sn11x Nb2 O61x , x50.0, 0.5, and 1.0, are reported. The materials have been characterized by bulk chemical analysis, single-crystal and powder X-ray di4raction, and 119Sn Mossbauer and 93Nb and 119Sn solid-state NMR spectroscopies. SnNb2 O6 is a synthetic analog of the rare mineral foordite. Red Sn2 Nb2 O7 crystallizes in a pyrochlore structure with a510.5386 A. 119Sn Mossbauer reveals the presence of both Sn(II) and Sn(IV) in pyrochlore samples. 119Sn MAS NMR spectroscopy supports the presence in synthetic foordite of Sn(II) in eight-fold coordination. The six-coordinated Sn(IV) and eight-coordinated Sn(II) 119Sn MASNMRresonances are not resolved in the Sn2 Nb2 O7 pyrochlore spectrum. 93Nb NMR indicates a fairly distorted local environment for niobium in synthetic foordite, much more so than in the Sn2 Nb2 O7 pyrochlore.
Descrição
Palavras-chave
oxides pyrochlore tin niobate crystal structure 119Sn and 93Nb NMR 119Sn Mossbauer