STRUCTURE AND DEVITRIFICATION CHEMISTRY OF RE(PO3)3 (RE=La, Pr, Nd, Gd, Dy, Y) METAPHOSPHATE GLASSES
2002 Volume 13 Pages 137-146
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2002 Volume 13 Pages 137-146
The devitrification and structure of RE(PO3)3 (RE=La, Pr, Nd, Gd, Dy, Y) glasses are studied by infrared spectroscopy, X-ay diffraction and differential thermal analysis. The results from devitrification experiments show that RE(PO3)3 glasses (regardless of the size of RE3+) crystallize first to give monoclinic Yb(PO3)3 type crystals. The IR spectra of devitrified. La, Pr, and Nd samples differ, however, from those of Gd, Dy and Y in the range of symmetric POP stretching frequencies. To unravel the differences demonstrated in the IR spectra of devitrified RE(PO3)3 we performed preliminary Rietveld refinement on the crystal structure of the “metastable” Nd(PO3)3 [monoclinic, P21/c a=11.468(4) Å, b=20.438(7) Å, c=10.256(3) Å, β=97.11(1)0, Z=12] and compared it to previously reported Yb(PO3)3. Comparisons between the IR spectra of the series of RE(PO3)3 glasses and related crystals show that VasPO2 and dasPOP stretching frequencies shift in the spectra of glasses which is explained with the alteration of chain conformation and subsequent decrease in POP bond angles in the glass network.
