EFFECT OF NATURAL ZIRCON POWDER AS SEEDS ON THE GEL SYNTHESIS OF ZIRCON POWDER

Effect of naturally occurring zircon powder as seeds for the gel synthesis of ultrafine zircon (ZrSiO4) powder was studied by XRD and TEM methods. The results reveal that even a small amount of natural zircon sand in the precursor gel has a remarkably favourable effect on the formation of zircon with a lowering of the calcination temperature by about 100-150 degrees C. Almost single-phase zircon powder, with particle size of 0.2-0.3 mu m, can be obtained from the precursor gel seeded by 3 mol% zircon sand particles when calcined at 1400 degrees C for 2 h. The mechanism of zircon formation is heterogeneous nucleation on the free surface of the seeds.