17O Solid-state NMR examination of La2O3 formation

Abstract

Solid-state ¹⁷O magic-angle spinning (MAS) NMR spectroscopy has been used to study the formation of hexagonal La₂O₃ from both dehydroxylation of La(OH)₃ and a sol–gel route starting from lanthanum isopropoxide. Both routes proceed via the formation of the oxyhydroxide [LaO(OH)] which is not commonly observed for other simple oxides. ¹⁷O NMR spectroscopy is very sensitive to structural change even in amorphous samples and the resonances of specific phases are assigned elucidating the chemical shift ranges of the local oxygen coordinations in these materials. The quadrupolar coupling constant for the OLa₄ site in La₂O₃ is determined by the application of satellite transition NMR spectroscopy.