GROWTH OF NEODYMIUM HEPTAMOLYBDATE CRYSTALS IN SILICA-GELS AT AMBIENT-TEMPERATURES

The growth of neodymium heptamolybdate crystals is described in the sy stem Nd(NO3)3-MoO3-NH4OH-HNO3-Na2SiO3 using a single gel, single tube technique. The influence of pH, gel concentration and concentration of upper and lower reactants on the size, quality and nucleation density of the crystals is discussed. The techniques of concentration program ming and seeded growth are used to enhance the crystal size. Factors i nfluencing the formation of Liesegang rings during the growth are desc ribed. Both gel pH and temperature are observed to have a remarkable e ffect on Liesegang ring formation. The grown crystals are observed to exhibit varied morphology, for example platelets, cuboids, spherulites , crystal aggregates and coalesced crystals.