Molten salt syntheses yield a rich variety of metal selenophosphate compounds which have a wide range of 31P T1 longitudinal relaxation times (20-3000 s). There is a qualitative positive correlation between squared dipolar couplings and 1/T1, suggesting that these interactions contribute to relaxation. However, two of the compounds, K 2CdP2Se6 and Rb2CdP 2Se6, have T1 which are significantly shorter than what is expected from dipolar couplings. The ESR spectra of these compounds show the presence of unpaired electrons which may accelerate the rate of 31P relaxation. The importance of relaxation in application of 31P NMR to these systems is demonstrated in analysis of the mixture of crystalline products formed in a Ag4P2Se6 synthesis. At short relaxation delays, the NMR intensities are non-quantitative and overestimate the concentration of an Ag7PSe6 impurity.
ASJC Scopus subject areas
- Nuclear and High Energy Physics