Partial thermodynamic functions of aluminum in sodium aluminum vanadium beta-bronzes

The partial thermodynamic functions of Al in the beta-bronzes Na2-yAlyV12O3 0 (0 < y less than or equal to 0.7), Na2AlyV12O30 (0 < y less than or equal to 1.4), and Na1.3AlyV12O30 (0 < y less than or equal to 2.1) were determi ned as a function of composition in the temperature range 294-348 K. The De lta(G)over bar (Al), Delta(H)over bar (Al), and Delta(S)over bar (Al) of th e bronzes were found to vary in a complex manner with Al content, passing t hrough extrema near y = 1 as a result of the structural ordering of Al3+ io ns. The temperature dependences of Delta(G)over bar (Al) show changes in sl ope between 303 and 318 K, attributable to redistribution of the Al3+ ions over the possible crystallographic sites in the beta-bronze structure.