Crystal structure and thermal characterization of cadmium oxalate [CdC2O4 · 3H2O] and barium-doped cadmium oxalate [Ba0.5Cd0.5(C2O4)2 · 5H2O] single crystals grown in silica gel

Pure cadmium oxalate trihydrate (COT) and barium added cadmium oxalate (BCO) single crystals were grown by controlled diffusion of Cd2+ and Ba2+ ions in silica gel at ambient temperature. A single test tube technique coupled with gel aging conferred maximum size crystals by controlling the nucleation rate. It was found that the pH and age of the gel greatly influenced the crystal quality, their size and transparency. Grown crystals CdC2O4 · 3H2O and Ba0.5Cd0.5(C2O4)2 · 5H2O were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and thermal analysis. Effect of barium dopant on the growth and morphology of cadmium oxalate was studied. Pure cadmium oxalate crystallized in triclinic system and the barium-doped cadmium oxalate crystallized in hexagonal system with massive changes in their unit cell parameters. The infrared spectrum revealed the presence of oxalate ligands and water of hydration in both the pure and barium-doped crystals. Thermal analysis showed that the grown crystals were dehydrated thermally even from lower temperatures and the doped crystals were found more stable.

Pure cadmium oxalate trihydrate (COT) and barium added cadmium oxalate (BCO) single crystals were grown by controlled diffusion of Cd2+ and Ba2+ ions in silica gel at ambient temperature. Crystallization of cadmium oxalate favors the Liesegang ring formation, whereas on barium doping ring formation is not observed. Cadmium oxalate is indexed for triclinic structure and on addition of barium in the cationic proportion 1:1, triclinic structure is transformed to hexagonal morphology.Growth kinetics revealed dependence of growth parameters like gel pH, gel aging, precursor concentrations and their supersaturation. In acidic pH, grown crystals were comparatively pure than the crystals grown on high pH gels. Gel aging controls the diffusion of cations thereby controls the nucleation. Structural morphology reveled transformation from triclinic to hexagonal on adding barium to the cadmium oxalate crystal lattice. Infrared and thermal studies confirmed the purity of the crystals without additional impurities.Figure optionsDownload as PowerPoint slide