Investigation dielectric studies and second harmonic generation (SHG) efficiency of bisthiourea cobalt malonate and bisthiourea nickel malonate: A novel semiorganic nonli ear optical materials

摘要

A new semiorganic NLO materials viz. bisthiourea cobalt malonate (BTCoM) and bisthiourea nickel malonate (BTNiM) have been synthesized by solvent free mechanochemical method. They are characterized by CHNS, FTIR, TG/DTA/DSC, XRD and UV-VIS. spectroscopy. Chemical composition was confirmed by chemical and CHNS analysis. FTIR studies confirmed the presence of various functional groups and coordination of metal ion to thiourea through sulphur atom. Thermal behavior has been investigated by using TG, DTA and DSC showing BTNiM is more stable. The X-ray data suggest that synthesized compounds are polycrystalline in nature. Transmittance spectra reveal that lower cut-off wavelength for BTCoM is 296.52nm and for BTNiM is 297.81nm, thus materials have good optical transmission in entire visible region. Magnetic measurements were carried out by Faraday method. The dielectric measurements of material with varying frequencies at room temperature were studied. The dielectric constant and dielectric loss decreases with increase in frequency for both compounds. These lower values at higher frequency are a desirable property to enhance the second harmonic generation (SHG) efficiency. The SHG conversion efficiency measured by Kurtz-Perry powder technique was found to be higher for BTCoM than BTNiM which defines the nonlinear optical nature of materials and their suitability for NLO applications.