For each phase, the chemical shift of the fully coalesced peak also gives information as to the residence time of mobile O 2-ions in O Bi environments vs. O V environments. The coalesced shift of 332 ppm for the Bi 0.913 V 0.087 O 1.587 phase corresponds to a ratio of 70:30 (O Bi :O V ), while the shift of 391 ppm for Bi 0.852 V 0.148 O 1.648 gives a ratio of 52:48 (O Bi :O V ). This result is intuitively reasonable given the higher concentration of V in Bi 0.852 V 0.148 O 1.648 . Furthermore, the expected ratios of O Bi :O V sites calculated from the nominal stoichiometry values, assuming isolated VO 4 tetrahedra, (i.e., 79:21 for Bi 0.852 V 0.148 O 1.648 and 64:36 for Bi 0.913 V 0.087 O 1.587 ) are significantly larger than the actual ratios calculated from the coalescence data. This result suggests the VT-NMR data are sensitive to the presence of oxygen vacancies in the Bi-O sublattice and/or overcoordination of the VO 4 units. For Bi 0.852 V 0.148 O 1.648 , the relative number and/or residence time of O V sites is 33% larger than that expected solely from stoichiometry, whereas it is 43% larger than expected for Bi 0.913 V 0.087 O 1.587 , implying that the latter phase has a higher average V coordination.