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The Hydrogarnets Sr 3 [ RE (OH) 6 ] 2 ( RE = Sc, Y, Ho – Lu): Syntheses, Crystal Structures, and their Thermal Decomposition to Ternary Rare‐Earth Metal Oxides
Author(s) -
Albrecht Ralf,
Doert Thomas,
Ruck Michael
Publication year - 2020
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.202000031
Subject(s) - strontium , crystal structure , thermal decomposition , scandium , crystallography , ternary operation , alkaline earth metal , paramagnetism , decomposition , acentric factor , oxide , chemistry , materials science , metal , inorganic chemistry , physics , organic chemistry , quantum mechanics , computer science , programming language
Seven rare‐earth metal hydrogarnets Sr 3 [ RE (OH) 6 ] 2 ( RE = Sc, Y, Ho‐Lu) were synthesized at about 200 °C starting from the respective RE 2 O 3 and Sr(NO 3 ) 2 in a KOH hydroflux with a water‐to‐base ratio of 1.6. All seven hydrogarnets crystallize in the acentric variant (space group I 4 3 d ) of the cubic garnet structure. The crystal structures of the hydrogarnets Sr 3 [ RE (OH) 6 ] 2 , the differences between both structural variants including a simple method to distinguish between them, and the crystal‐chemical classification with respect to other known strontium hydrogarnets are discussed. The rare‐earth hydrogarnets can be used as carbon‐free precursors for magnetic oxides. Starting at about 300 °C, the hydrogarnets decompose in a two‐ or three‐step dehydration to Sr RE 2 O 4 and SrO. The decomposition of Sr 3 [Sc(OH) 6 ] 2 follows a different mechanism and was studied by in‐situ temperature‐dependent powder X‐ray diffraction up to 1000 °C. The final decomposition products were SrO and an unknown strontium scandium oxide, with an X‐ray pattern similar to BaSc 2 O 4 . Magnetic measurements of the erbium and ytterbium hydrogarnets revealed paramagnetic behavior down to 1.8 K.