Phase Equilibria in the Ln2O3–V2O3–V2O5 (Ln=Pr, Tb, and Y) Systems at 1200 °C
- 1 March 1985
- journal article
- Published by Oxford University Press (OUP) in Bulletin of the Chemical Society of Japan
- Vol. 58 (3) , 948-956
- https://doi.org/10.1246/bcsj.58.948
Abstract
The phase equilibria in the systems, Pr2O3–V2O3–V2O5, Tb2O3–V2O3–V2O5, and Y2O3–V2O3–V2O5, were established at 1200 °C by changing the oxygen partial pressure from −1.20 (in the CO2) to 7.50 in −log (PO2/Pa) for Pr2O3 and Tb2O3 systems, and from −4.32 (in the air) to 7.50 in −log (PO2/Pa) for Y2O3 system. In the first system 0.81Pr2O3·0.19V2O5(A) and 3Pr2O3·V2O5(B), in the second 0.81Tb2O3·0.19V2O5(A′), and in the last one 4Y2O3·V2O5(A″) were stable in addition to Ln2O3, LnVO4, LnVO3, VnO2n−1 (n=2–7, and Ln means Pr, Tb, and Y), and VO2 under the present experimental conditions. On the basis of the established phase diagrams, the standard Gibbs energies (ΔG°) of reactions appeared in the systems were calculated. Compounds A, B, PrVO3, A′, A″, and LnVO4 have nonstoichiometric compositions. ΔG° values for the reactions and crystallographic values of the compounds were represented as a function of the ionic radius of lanthanoid (including Y) elements.Keywords
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