Journal article

Publication year: 2016

Pages: 23-34

Journal: Applied Catalysis B: Environment and Energy

Volume number: 197

DOI Link: https://doi.org/10.1016/j.apcatb.2016.03.049

Publisher: Elsevier

Abstract: 

The κ-Ce2Zr2O8 phase has been synthesized starting from t-Ce0.5Zr0.5O2 solid solution which is reduced by hydrogen at high temperatures to form the pyrochlore Ce2Zr2O7 phase (pyr-Ce2Zr2O7) with high degree of ordering of the cationic sublattice. The final step in the synthesis of the κ-Ce2Zr2O8 phase includes a mild re-oxidation of pyr-Ce2Zr2O7 at around 600 °C under atmospheric conditions. Yet, the synthesis of phase-pure κ-Ce2Zr2O8 phase (phase-pure and with highest ordering) is still not settled since most of the previous studies used reduction temperatures of 1300 °C and below. We show in this contribution that 1300 °C is not sufficient to warrant the preparation of phase-pure pyr-Ce2Zr2O7 and κ-Ce2Zr2O8, but that rather temperatures as high as 1500 °C are required to assure phase purity of both phases. This conclusion is drawn from extended X-ray diffraction and X-ray absorption spectroscopy analyses together with Raman spectroscopy, providing in-depth details of the structure on the level of both, the evolution of the special periodic structure and the coordination of the metal atoms.The κ-Ce2Zr2O8 phase has been synthesized starting from t-Ce0.5Zr0.5O2 solid solution which is reduced by hydrogen at high temperatures to form the pyrochlore Ce2Zr2O7 phase (pyr-Ce2Zr2O7) with high degree of ordering of the cationic sublattice. The final step in the synthesis of the κ-Ce2Zr2O8 phase includes a mild re-oxidation of pyr-Ce2Zr2O7 at around 600 °C under atmospheric conditions. Yet, the synthesis of phase-pure κ-Ce2Zr2O8 phase (phase-pure and with highest ordering) is still not settled since most of the previous studies used reduction temperatures of 1300 °C and below. We show in this contribution that 1300 °C is not sufficient to warrant the preparation of phase-pure pyr-Ce2Zr2O7 and κ-Ce2Zr2O8, but that rather temperatures as high as 1500 °C are required to assure phase purity of both phases. This conclusion is drawn from extended X-ray diffraction and X-ray absorption spectroscopy analyses together with Raman spectroscopy, providing in-depth details of the structure on the level of both, the evolution of the special periodic structure and the coordination of the metal atoms.

Harvard Citation style: Urban, S., Dolcet, P., Möller, M., Chen, L., Klar, P., Djerdj, I., et al. (2016) Synthesis and full characterization of the phase-pure pyrochlore Ce2Zr2O7 and the κ-Ce2Zr2O8 phases, Applied Catalysis B: Environment and Energy, 197, pp. 23-34. https://doi.org/10.1016/j.apcatb.2016.03.049

APA Citation style: Urban, S., Dolcet, P., Möller, M., Chen, L., Klar, P., Djerdj, I., Gross, S., Smarsly, B., & Over, H. (2016). Synthesis and full characterization of the phase-pure pyrochlore Ce2Zr2O7 and the κ-Ce2Zr2O8 phases. Applied Catalysis B: Environment and Energy. 197, 23-34. https://doi.org/10.1016/j.apcatb.2016.03.049