CONTROLLED COMBUSTION SYNTHESIS AND PROPERTIES OF FINE-PARTICLE NASICON MATERIALS

Fine-particle NASICON materials, Na1+xZr2P3-xSixO12 (where x = 0.0, 0. 5, 1.0, 1.5, 2.0 and 2.5), have been prepared by controlled combustion of an aqueous solution containing stoicthiometric amounts of sodium n itrate, zirconyl nitrate, ammonium perchlorate, diammonium hydrogen ph osphate, fumed silica and carbonohydrazide. Formation of NASICON has b een confirmed by powder XRD, Si-29 NMR and IR spectroscopy. These NASI CON powders are fine (average agglomerate size 5-12 mum) with a surfac e area varying from 8 to 30 m2 g-1. NASICON powders pelletized and sin tered at 1100-1200-degrees-C for 5 h achieved 90-95% theoretical densi ty and show fine-grain microstructure. The coefficient of thermal expa nsion of sintered NASICON compact was measured up to 500-degrees-C and changes f rom -3.4 x 10(-6) to 4.1 x 10(-6) K-1. The conductivity of Sintered Na3Zr2PSi2O12 compact at 300-degrees-C is 0.236 OMEGA-1 cm-1.