The room temperature 31 P NMR spectra of Bi 0.852 P 0.148 O 1.648 comprise a single broad resonance that narrows with increasing temperature (Figure ), allowing us to distinguish four different local environments. We assign these linewidth changes to the influence of nearby oxygen motion that enters the fast motional regime at high temperature and thus no longer broadens the 31 P resonances, a result that concurs with the narrowing linewidths seen in the corresponding O spectra. At high temperatures, the four distinct P resonances reflect small changes in the number and arrangement of nearby Bi and P atoms, in good agreement with the four reported crystallographic P sites in the monoclinic Bi 0.852 P 0.148 O 1.648 structure. This same resolution is not achieved in the V spectra, which is ascribed to some second-order quadrupolar line broadening of 51 V (I = 7/2) that persists even at high temperatures, as well as most likely increased disorder of the VO x polyhedra as compared to PO 4 .