Gadolinium Neodymium Oxalate (GNO) single crystals were grown in hydrosilica gel by the diffusion of a mixture of aqueous solutions of the respective rare earth nitrates into a gel, impregnated with oxalic acid, in a test tube. Pink, transparent, hexagonal GNO crystals were obtained on optimization of growth parameters. The crystals are found to be monoclinic by the XRD analysis. The presence of water of hydration and carboxylic group in the grown crystals was confirmed by IR analysis. EDAX analysis confirmed the presence of Gd and Nd in the grown samples. The thermal decomposition behavior of the grown crystals were studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The thermal analysis results concur with the proposed crystal structure.

Single crystals of Gadolinium Samarium Oxalate (GSO) are grown by gel method. The crystals are pale yellowish in colour. Morphology and size of the crystals are found to depend on pH of the medium, gel density, concentration of the reactants and acidity of the feed solution. The crystallinity of the grown sample was confirmed by X-ray diffraction studies and the lattice parameters were determined. X-ray diffractogram shows well defined peaks. IR spectrum confirms the presence of water molecules and carboxylic group. EDAX analysis confirms the presence of Gd and Sm in the sample. The thermal decomposition behaviour of the crystal was analysed using TGA and DTA studies.

Good optical grade single crystals of pure, Cd 2+ and Mg 2+ doped Manganese Mercury Thiyocyanate (MMTC) crystals are grown by slow solvent evaporation technique at room temperature. Single crystal XRD studies reveal that the incorporation of metallic dopants has not changed the structure of the parent crystal. The SHG efficiencies of the pure and doped samples of MMTC are measured by Kurtz Perry powder method and the results are compared with urea. It is evident from microhardness study that the presence of dopants has increased the mechanical strength of MMTC crystal. The TG/DTG studies confirm that the thermal decomposition temperatures of pure (353°C), Mg 2+ doped (363°C ) and Cd 2+ doped (365°C) MMTC are relatively high when compared to other NLO crystals of the same family.

iodine and hydrogen iodide as transporting agents has been reported in this paper. Results give range of temperature for the iodide transport and prevention of starting material formation (elemental transport) in the growth zone. From the range of temperature for the growth of crystals, selected source zone and growth zone temperatures with a differential of 100 0 C are also listed. Referring the data listed in the tables can grow good quality crystals.

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