High temperature stability of oxysulphides containing Ce3+ and Y3+ ions

Akila, R. ; Jacob, K. T. (1988) High temperature stability of oxysulphides containing Ce3+ and Y3+ ions Ceramics International, 14 (3). pp. 147-152. ISSN 0272-8842

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Official URL: http://www.sciencedirect.com/science/article/pii/0...

Related URL: http://dx.doi.org/10.1016/0272-8842(88)90003-X


Standard Gibbs energies of formation of oxysulfides of cerium and yttrium from their respective oxedes were determined using solid oxide galvanic cells incorporating calcia-stabilized zirconia as the electrolyte in the temperature range 870–1120 K. The sulfur potential over the electrode containing the oxide and oxysulfide was fixed by a buffer mixture of Ag + Ag2S. A small amount of CaH2 was added to the buffer to generate an equilibrium ratio of H2S and H2 species in a closed system containing the buffer and the electrode. The sulfur potential is transmitted to the electrode via the gas phase. The results can be summarized by the equations 2(CeO2)+1/2(S2)→(Ce2O2S)+(O2) ΔG°=430600−109·7T(±400)J mol−1 (Y2O3)+1/2(S2)→(Y2O2S)+1/2(O2) ΔG°=114780−1·45T(±200)J mol−1 The values are compared with data reported in the literature. The stability field diagram for the Ce2O2S system has been developed using the results of this study for Ce2O2S and data for other phases from the literature.

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