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VORON’KO et al.
(Fig. 6, spectrum 9, line f). In addition to line f, the
Raman spectrum of molten phosphorus pentoxide
shows a shoulder in the νs(PO) region, at the frequency
of line d in the spectrum of the R = 1/2 melt, and a
broad, weak, polarized band h in the frequency range of
the terminal and middle groups of short polyphosphate
chains. This attests to partial anion depolymerization in
molten phosphorus pentoxide, which cannot be
accounted for in terms of random anion rearrangement,
which would lead to the formation of groups in which
phosphorus–oxygen tetrahedra share the four corners
with one another. This is, however, impossible for pen-
tavalent phosphorus [7]. The most likely reason for the
partial anion depolymerization in molten P2O5 is the
presence of residual water in the starting material, char-
acteristic of phosphorus pentoxide [7].
REFERENCES
1. Rawson, H., Inorganic Glass-Forming Systems, Lon-
don: Academic, 1967. Translated under the title Neor-
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2. Abello, L., Husson, E., Repelin, Y., and Lucazeau, G.,
Vibrational Spectra and Valence Force Field of Crystal-
line V2O5, Spectrochim. Acta, 1983, vol. 39, no. 7,
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3. Voron’ko, Yu.K., Kudryavtsev, A.B., Osiko, V.V., and
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pp. 559–561.
Consider now the possible manifestations of ran-
dom anion rearrangement in the Raman spectra of mol-
ten alkali vanadates. As seen in Fig. 2b, the low- and
high-frequency wings of the composite Raman band in
the νs(PO3) region of the pyrovanadate anion lie in the
5. Balagina, G.M., Banishev, A.F., Voron’ko, Yu.K., et al.,
Raman Scattering Study of Phase Transformations in
Ln(PO3)3 Rare-Earth Polyphosphates, Izv. Akad. Nauk
SSSR, Neorg. Mater., 1985, vol. 21, no. 5, pp. 712–719.
frequency ranges of the νs(VO4) line of the orthovana-
6. Voron’ko, Yu.K., Gorbachev, A.V., and Sobol’, A.A.,
Structure of Chain Phosphate Anions in Alkali Poly-
phosphate Crystals, Glasses, and Melts: A Raman Scat-
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date anion and the νs(VO4) line of the terminal groups
of polyvanadate chains (Fig. 3b). In the Raman spec-
trum of molten lithium polyvanadate, the low-fre-
quency wing of the νs(VO2) line falls the νs(VO3)
region of the pyrovanadate anion (Fig. 5). Thus, ran-
dom anion rearrangement may also occur in vanadate
melts and shows up in their Raman spectra in the same
manner as that in molten alkali phosphates. However,
the large linewidth in the Raman spectra of vanadate
melts impedes detailed analysis of the structure of
anion groups, in contrast to phosphate melts. In partic-
ular, it accounts for the fact that the νs(VO) lines on the
high-frequency side of the νs(VO2) line, predicted by
the random anion rearrangement model, are missing in
the spectrum of molten lithium polyvanadate (Fig. 5).
7. Van Wazer, J.R., Phosphorus and Its Compounds, New
York: Interscience, 1958. Translated under the title Fos-
for i ego soedineniya, Moscow: Inostrannaya Literatura,
1962.
8. Harbach, F. and Fisher, F., Raman Spectra and Optical
Absorption Edge of Li3PO4 Single Crystals, Phys. Status
Solidi B, 1974, vol. 66, pp. 237–243.
9. Shannon, R.D. and Calvo, C., Refinement of the Crystal
Structure of Low Temperature Li3VO4 and Analysis of
Mean Bond Length in Phosphates, Arsenates, and Vana-
dates, J. Solid State Chem., 1973, vol. 6, pp. 538–549.
10. Lazarev, A.N., Mirgorodskii, A.P., and Ignat’ev, I.S.,
Kolebatel’nye spektry slozhnykh okislov (Vibrational
Spectra of Mixed Oxides), Moscow: Nauka, 1975.
CONCLUSIONS
11. Ioffe, V.A., Moskalev, V.V., Dmitrieva, L.V., et al., 51V
NMR Spectra of Zinc and Calcium Pyrovanadates, Fiz.
Tverd. Tela (Leningrad), 1975, vol. 17, pp. 3081–3083.
Molten alkali and alkaline-earth vanadates contain
vanadium–oxygen groups such as isolated tetrahedra,
pyrovanadate groups, and chain anions, similar to the
structural units of phosphate melts. In ultravanadate
melts, the tetrahedral structure of vanadium–oxygen
groups is disrupted, in contrast to ultraphosphate melts.
12. Ingri, N. and Brito, F., Equilibrium Studies of Polyan-
ions: VI. Polyvanadates in Alkaline Na(Cl) Medium,
Acta Chem. Scand., 1959, vol. 13, pp. 1971–1996.
The difference in electronic configuration between
phosphorus and vanadium is responsible for the large
width of the characteristic lines of tetrahedral groups in
the Raman spectra of vanadate melts compared to phos-
phate melts. Random anion rearrangement occurs in
both phosphate and alkali vanadate melts and can be
investigated in detail by Raman spectroscopy.
13. Bues, V.W. and Gehrke, H.-W., Schwingungsspektren
von Schmelzen, Glasern und Kristallen des Natrium-di-
und Tetraphosphates, Z. Anorg. Allg. Chem., 1956,
vol. 288, pp. 291–323.
14. Voron’ko, Yu.K., Kudryavtsev, A.B., Sobol’, A.A., and
Sorokin, E.V., High-Temperature Raman Spectroscopy:
A Tool for Probing Phase Transformations of Laser
Crystals, Tr. Inst. Obshch. Fiz., Akad. Nauk SSSR, 1991,
vol. 29.
ACKNOWLEDGMENTS
15. Gerding, H. and de Decker, H.C.J., The Raman Spec-
trum of Phosphorus Pentoxide, J. Rec. Trav. Chem.,
1945, vol. 64, pp. 191–193.
This work was supported by the Russian Foundation
for Basic Research, project no. 04-02-16482.
INORGANIC MATERIALS Vol. 41 No. 10 2005