Fabrication of Silica Gel Reinforced, Cadmium Oxalate based Extrinsic Crystalline Materials and their Characterization

Cobalt-lead mixed cadmium oxalate (CoLMCO) and zinc-lead mixed cadmium oxalate (ZnLMCO) extrinsic crystalline materials were grown in oxalic acid embedded silica hydrogel. In an optimized gel environment, the extrinsic Co2+-Pb2+ and Zn2+-Pb2+ combinations fit well in the parental Cd2+ vacancies and emerged as distinct CoLMCO and ZnLMCO novel materials. The inherent properties of CoLMCO and ZnLMCO crystals were characterized by analytical and spectroscopic methods. Energy dispersive X-ray (EDX) analysis attached with field emission scanning electron microscope (FESEM) was employed to identify the chemical composition and morphology of the crystals. Fourier transform infrared (FTIR) spectral analysis confirmed the presence of oxalate group, water of crystallization and metal-oxygen bonds in the crystals. Thermal studies confirmed two phases of decomposition and ensured stability up to 1112.78 ºC for CoLMCO crystals and 1071.65 ºC for ZnLMCO crystals in a metal-oxide state. Bragg’s diffraction patterns revealed the high crystallinity of the materials and observed triclinic geometry in them. The UV-visible spectral studies of CoLMCO and ZnLMCO crystals showed maximum transparency to visible light and absorption in the UV region, possessing absorption maximum Amax = 1.588 and 1.276; optical band gap energies Eg = 5.638 eV and 5.845 eV, respectively. The V-I characteristics of the prepared crystals unveiled a feeble current flow (nA), exhibiting linear variation with applied DC voltage (0-200 V) leading leakage resistances of 1.187 GΩ (CoLMCO) and 5.176 GΩ (ZnLMCO). Dielectric constants of mixed crystals varied inversely with applied frequency and became almost stable at the mid-radio frequency range.