MORPHOLOGY OF RARE-EARTH POLYMERIC ELECTROLYTES

The usual two-solvent casting technique was used to prepare a series o f poly(ethylene oxide), PEG, and poly(propylene oxide), PPO, electroly tes containing trivalent salts of Eu, Nd, and Pr with concentrations b etween n = 80 and n = 3 (n is the number of ether oxygen atoms in the polymer chain per lanthanide cation). The films were characterized by differential scanning calorimetry, scanning electron microscopy/energy -dispersive X-ray microanalysis, and X-ray powder diffraction. The EU( 3-) and pr(3-) electrolytes with n greater than or equal to 8 exhibit an endothermic peak around 65 degrees C, which is associated with the melting of crystalline PEG. Films with compositions 16 greater than or equal to n greater than or equal to 7 showed, in addition, a smaller endotherm around 60 degrees C, which results from a eutectic phase of PEO and PEO/salt complex. The highly concentrated PEO(n)EuBr(3) films, n less than or equal to 6, are a glassy, transparent, and fragile mat erials when no traces of water are detected. The stoichiometry of the high-melting-point crystalline complex observed for these EU(3+) elect rolytes appears to be close to an oxygen-cation ratio of 3:1. The morp hology of the Nd3+ electrolytes was found to be independent of the sal t concentration. These films are characterized by the presence of a cr ystalline PEO phase and, probably, a nonstoichiometric PEO-NdCl3 compl ex. PPO-EuBr3 electrolytes are predominantly amorphous and formation o f a salt-rich complex phase was also observed at high salt concentrati ons.