PREPARATION OF CUZR2P3O12 FROM ALKOXIDE-DERIVED GELS - PHASE FORMATION AS A FUNCTION OF HEAT-TREATMENT

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 ( {Mathematical expression}. 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 {Mathematical expression}-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. © 1990 Chapman and Hall Ltd.