Preparation of CuZr2P3O12 from alkoxide-derived gels: phase formation as a function of heat treatment |
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Authors: | E. Christensen J. H. Von Barner J. Engell N. J. Bjerrum |
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Affiliation: | (1) Chemistry Department A, Technical University of Denmark, Building 207, DK-2800 Lyngby, Denmark;(2) Institute of Mineral Industry, Technical University of Denmark, Building 204, DK-2800 Lyngby, Denmark |
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Abstract: | The phase formation in alkoxide gels with composition corresponding to CuZr2P3O12 has been studied as a function of gel preparation and heat treatment. Two preparational methods have been examined. The chemicals used include Cu(NO)3 · 3H2O, Zr(n-OC3H7)4 and either P2O5 or H3PO4, respectively. The P2O5 method results in the formation of di-phase gels. Heat treatment of these invariably gives multi-phase materials. Gels prepared by the H3PO4 method are completely amorphous and can be converted into porous glasses by heating to 500 °C. Calcination in the range 650 to 750 ° C results in the formation of a new CuZr4P6O24 phase (. Later, this prevents formation of mono-phase materials during heating to 1200 ° C. It is suggested that this behaviour is related to mixing of Cu2+ and Zr4+ in the normal copper and zirconium positions in the low-temperature-Nasicon. Calcination in the range 750 to 850 ° C results in the formation of the normal C2/c Cu2+-Nasicon which readily converts to mono-phase Cu+-Nasicon (CuZr2P3O12) above 880 ° C. Only gels calcined in the range 750 to 850 ° C are useful for the fabrication of mono-phase CuZr2P3O12 ceramics. |
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