STRUCTURE OF MIXED-ALKALI PHOSPHATE-GLASSES BY NEUTRON-DIFFRACTION AND RAMAN-SPECTROSCOPY

The structures of ion conducting mixed alkali metaphosphate glasses (L i2O)(x)-(Rb2O)(1-x)-2P(2)O(5) have been examined by neutron diffractio n and Raman spectroscopy. The results show that the short-range order of the phosphorous-oxygen network is almost independent of the composi tion. The only observable change is that the second peak in G(r), aris ing from the first O-O and P-P distances, increases slightly for incre asing rubidium concentration. The intermediate range order seems to in crease continuously with increasing rubidium content. The cation envir onments are distinctly different for Li+ and Rb+ and each of them rema ins about the same for all compositions. The nearest Li-O and Rb-O dis tances are determined to be 2.0+/-0.1 and 2.9+/-0.1 Angstrom, and the corresponding average coordination numbers are approximately 4 and 5, respectively. The Li+ and Rb+ ions are quasiuniformly distributed and we are not able to observe any-significant preference for either simil ar or dissimilar pairs of cations. The clearly different cation enviro nments suggest that the Li+ sites are energetically unfavorable to the Rb+ ions and vice versa. [S0163-1829(98)03437-7].