Investigation on erbium tartrate hexahydrate crystals grown in silica gel and its characterisation

Single and spherulitic crystal growth of erbium tartrate hexahydrate by silica gel diffusion technique is reported. The stoichiometric composition of the grown crystals is established to be [Er₂(C₄H₄O₆)₃(H₂O)₂]4H₂O, using energy dispersive X-ray analysis, CH analysis, Fourier transform infrared spectroscopy and thermo-analytical techniques. Using single and powder X-ray diffraction techniques from which it is established that the crystal falls under tetragonal system and non-centrosymmetric space group with lattice parameters as: a = b = 5.835 Å, and c = 35.392 Å; α = β = γ = 90°. The volume of the unit cell V = 1204.99 ų. Scanning electron microscopy reveals the morphology of the single crystals with habit faces {100}, {010}, and {001}. The surface morphology and internal structure of the spherulites of erbium tartrate hexahydrate have been studied by scanning electron microscopy. The results on growth kinetics are discussed using Frank’s relation, which leads to non-linear time–size relations. The non-linearity supports the fact that the concentration or supersaturation does not remain constant during the course of crystallization. The thermal behaviour of the crystals is described on the basis of results obtained on application of thermo-analytical techniques.