ELECTROCHEMICAL SODIUM INSERTION EXTRACTION IN NA-2(MOOPO4)(2)(HPO4)CENTER-DOT-YH(2)O (Y = 2, 0)/

The electrochemical sodium insertion and extraction of the phosphomoly bdates Na-2(MoOPO4)(2)(HPO4).gamma H2O (y = 2, 0) is reported. Both co mpounds show a similar behaviour upon electrochemical sodium extractio n, while the insertion reaction is notably different for each host com pound. During the charge/discharge of electrochemical cells the existe nce of new phases Na2 + x(MoOPO4)(2)(HPO4). 2H(2)O with compositions - 0.7 < x < -0.4, and 0.75 < x < 0.9, as well as Na2 + x(MoOPO4)(2)(HPO4 ) with -1 < x < -0.75 and 2.6 < x < 3.2 has been detected. A member of each solid solution has been synthesised and preliminarily structural ly characterised by powder X-ray diffraction. Although all of these ne w phosphomolybdates present a similar monoclinic structure, the unit c ell volume increases progressively with the introduction of sodium and water in the tunnels. Magnetic susceptibility measurements have also been performed in order to follow the electrochemical process.