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 combustion of aqueous heterogeneous mixtures of stoichiometric amounts of metal nitrate, zirconyl nitrate, niobium phosphate, diammonium hydrogen phosphate, ammonium perchlorate and carbohydrazide (CH) at 400 degrees C. The formation of NASICON materials was confirmed by powder X-ray diffraction (XRD), IR, solid-state (P-31) NMR spectroscopy and thermal expansion coefficient measurements. The combustion-synthesized NASICON powders have an average agglomerate size of 9-13 mu m with a specific surface area varying from 8 to 28 m(2) g(-1). The powders pelletized and sintered in the range 1100-1200 degrees C for 5 h achieved 95-97% theoretical density and showed fine-grain microstructure. The coefficient of thermal expansion of a sintered compact was measured up to 500 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.