PHASE EQUILIBRIA IN THE Yb2O3-P2O5-H2O SYSTEM: SYNTHESIS AND CHARACTERIZATION OF YTTERBIUM PHOSPHATES
2005 Volume 19 Pages 234-239
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2005 Volume 19 Pages 234-239
Using the thin-layer technique, phase equilibria in the Yb2O3-P2O5-H2O system have been studied within the temperature range of 20-300°C at the molar ratios P2O5: Yb2O3=(3÷10):1. The diagram of the crystallization fields for stable phases, YbH3(PO4)2·0.5H2O, YbH3(PO4)2, Yb3H5(PO4)2(P2O7)2, YbHP2O7, and Yb(PO3)3 (form II), has been constructed. Preliminary XRD studies have been performed for powder samples of YbH3(PO4)2 (monoclinic unit cell with a=10.989(2), b=6.858(2), c=9.123(2)Å; β=101.72(2)°), Yb3H5(PO4)2(P2O7)2 (tetragonal unit cell with a=6.884(1), c=17.554(2)Å), and YbHP2O7 (orthorhombic unit cell with a=11.994(1), b=6.870(1), c=6.846(1)Å). it was found that increasing temperature and/or decreasing water content cause a consecutive crystallization of ytterbium phosphates in the followlng order: YbH3(PO4)2·2H2O, YbH3(PO4)2·0.5H2O, YbH3(PO4)2, Yb3H5(PO4)2(P2O7)2, YbHP2O7, Yb(PO3)3-C or Yb4(P4O12)3-A, and Yb(PO3)3-II.
