Infrared and raman spectra of Ga2O3-P2O5 glasses

The structure of xGa(2)O(3)(1 - x)P2O5(0.15 less than or equal to x less th an or equal to 0.4) glasses is studied by infrared (IR) and Raman spectrosc opy. The results of quantitative electron microprobe analysis reveal that t wo sets of glasses are formed with compositions corresponding to the galliu m meta and pyrophosphates. Crystalline Ga(PO3)(3) metaphosphate is also obt ained and its IR and Raman spectra recorded in order to examine the spectra l differences glass --> crystal. The IR spectra of metaphosphate glasses sh ow bands at 1250, 930, 775 and 485 cm(-1) which, are assigned to the nu asP O2, nu asPOP, nu sPOP and delta PO2 modes of the metaphosphate chain. In th e Raman spectra are found patterns due to symmetric modes of PO2 terminal a nd POP bridging bonds as well as features due to vibrations of GaO4 tetrahe dra and Ga-O-P bridges. Comparisons of the spectra of glasses with those of the crystal indicate that the interaction of Ga with the poly phosphate an ions is more covalent in the glasses. The bands observed in the spectra of pyrophosphate glasses provide evidence for the involvement of ortho-, pyro- and polyphosphate groupings in the glass structure. The Raman spectra of b oth sets of glasses display intense low frequency bands, which we assigned to a symmetric bending of Ga-O-P bridging bonds involving four-coordinated gallium atoms. It is concluded that structure of Ga2O3-P2O5 glasses is a hi ghly polymerized network consisting of a variety of phosphate anions cross- linked by GaO4 tetrahedra. This account on glass structure is consistent wi th the great glass forming ability of the compositions studied. (C) 2001 El sevier Science B.V, All rights reserved.