COMBUSTION SYNTHESIS AND PROPERTIES OF THE NASICON FAMILY OF MATERIALS

The fine-particle NASICON family of materials, MZr(2)P(3)O(12) (where M=Na, K, 1/2Ca and 1/4Zr) and NbZrP3O12, have been prepared by the com bustion of aqueous heterogeneous mixtures of stoichiometric amounts of metal nitrate, zirconyl nitrate, niobium phosphate, diammonium hydrog en phosphate, ammonium perchlorate and carbohydrazide (CH) at 400 degr ees C. The formation of NASICON materials was confirmed by powder X-ra y diffraction (XRD), IR, solid-state (P-31) NMR spectroscopy and therm al expansion coefficient measurements. The combustion-synthesized NASI CON powders have an average agglomerate size of 9-13 mu m with a speci fic surface area varying from 8 to 28 m(2) g(-1). The powders pelletiz ed and sintered in the range 1100-1200 degrees C for 5 h achieved 95-9 7% theoretical density and showed fine-grain microstructure. The coeff icient of thermal expansion of a sintered compact was measured up to 5 00 degrees C and ranged from -1.5 x 10(-6) degrees C-1 to 1.0 x 10(-6) degrees C-1 depending on the composition.