SYNTHESIS AND CHARACTERIZATION OF H-MGXWO3 AND MGXW18O49 AND THEIR INTERCALATION WITH LITHIUM

New tungsten bronzes, MgxWO3 and MgxW18O49, have been synthetized by m agnesium chemical insertion reaction. For the former case, two blue br onzes with composition Mg0.09WO3 and Mg0.15WO3 have been isolated thro ugh a topotactic reaction that keeps the parent hexagonal structure un altered. In the case of W18O49, a new compound with composition Mg0.9W 18O49 and lattice parameters close to those of W18O49 has been synthet ized. We have also studied the electrochemical lithium insertion in h- MgxWO3 and MgxW18O49. In this way, different phases have been detected in the systems Li-MgxWO3 and Li-MgxW18O49 and a relationship between the maximum quantity of lithium inserted and the magnesium content is deduced and discussed in terms of the ionic potential of the intercala ted ions.