Targeting Vacancies in Nitridosilicates: Aliovalent Substitution of M2+ (M=Ca, Sr) by Sc3+ and U3

Based on the known linking options of their fundamental building unit, that is the SiN4 tetrahedron, nitridosilicates belong to the inorganic compound classes with the greatest structural variability. Although facilitating the discovery of novel Si–N networks, this variability represents a challenge...

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Bibliographic Details
Published in:Angewandte Chemie 2019-01, Vol.131 (3), p.850-853
Main Authors: Bielec, Philipp, Eisenburger, Lucien, Deubner, H. Lars, Günther, Daniel, Kraus, Florian, Oeckler, Oliver, Schnick, Wolfgang
Format: Article
Language:English
Subjects:
Actinides
Calcium
Chemistry
Immobilization
Inorganic compounds
Ion exchange
Lattice vacancies
Nitride
Nitridosilicate
Organic chemistry
Powder
Scandium
Strontium
Synchrotronstrahlung
Tetrahedra
Uran
Vacancies
Variability
X-ray diffraction
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Summary:Based on the known linking options of their fundamental building unit, that is the SiN4 tetrahedron, nitridosilicates belong to the inorganic compound classes with the greatest structural variability. Although facilitating the discovery of novel Si–N networks, this variability represents a challenge when targeting non‐stoichometric compounds. Meeting this challenge, a strategy for targeted creation of vacancies in highly condensed nitridosilicates by exchanging divalent M2+ for trivalent M3+ using the ion exchange approach is reported. As proof of concept, the first Sc and U nitridosilicates were prepared from α‐Ca2Si5N8 and Sr2Si5N8. Powder X‐ray diffraction (XRD) and synchrotron single‐crystal XRD showed random vacancy distribution in Sc0.2Ca1.7Si5N8, and partial vacancy ordering in U0.5xSr2−0.75xSi5N8 with x≈1.05. The high chemical stability of U nitridosilicates makes them interesting candidates for immobilization of actinides. Hoch kondensierte Nitridosilicate zeigen beachtliche thermische und chemische Stabilität, so wie ihre Stammverbindung Si3N4. Eine Strategie zur gezielten Einführung von Leerstellen in vorab synthetisierte Si‐N‐Netzwerke wurde entwickelt. Dies könnte nützlich für die Entwicklung von Ionenleitern oder für Anwendungen zur Lagerung radioaktiven Abfalls sein, da diese Materialien Ionen immobilisieren und gasförmige Produkte des radioaktiven Zerfalls absorbieren können.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201812460