Solid-state NMR and short-range order in crystalline oxides and silicates: a new tool in paramagnetic resonances.

Most applications of high-resolution NMR to questions of short-range order/disorder in inorganic materials have been made in systems where ions with unpaired electron spins are of negligible concentration, with structural information extracted primarily from chemical shifts, quadrupolar coupling parameters, and nuclear dipolar couplings. In some cases, however, the often-large additional resonance shifts caused by interactions between unpaired electron and nuclear spins can provide unique new structural information in materials with contents of paramagnetic cations ranging from hundreds of ppm to several per cent and even higher. In this brief review we focus on recent work on silicate, phosphate, and oxide materials with relatively low concentrations of paramagnetic ions, where spectral resolution can remain high enough to distinguish interactions between NMR-observed nuclides and one or more magnetic neighbors in different bonding configurations in the first, second, and even farther cation shells.

31P magic angle spinning NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: evidence of random cation distribution from paramagnetically shifted NMR resonances.

We present (31)P magic angle spinning nuclear magnetic resonance spectra of flux-grown solid solutions of La(1-x)Ce(x)PO4 (x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y(1-x)M(x)PO4 (M = V(n+), Ce(3+), Nd(3+), x between 0.