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Mechanical, dielectric and thermal analysis of semi-organic NLO materials

S. Gunasekaran, G. Anand, S. Kumaresan and S. Kalainathan

Semi organic crystals offer a variety of molecular structures by virtue of the changes brought out in selection of metals, ligand and coordination numbers. The diversity of molecular structure given an opportunity to tune the electronic properties and hence to exploit the linear and non linear optical properties. Efficient non-linear optical crystals bis thiourea manganese sulphate (BMTS), tris thiourea manganese sulphate (TMTS) and urea thiourea manganese sulphate (UTMS) have been grown by slow evaporation technique. All the three crystals belong to orthorhombic system. In the present work the mechanical, dielectric studies and thermal analysis of BMTS, TMTS and UMTS crystals have been studied and compared. Vicker’s micro hardness test was carried out to study the mechanical strength of the crystals. The Meyer’s index number (n) was calculated using Vickers’s micro hardness number. The change in concentration of thiourea does not have any impact on the mechanical strength of the crystals. The dielectric constant and dielectric loss were found to decrease when the frequency increased. Low dielectric constant and dielectric loss at higher frequency is a desirable property to enhance the SHG efficiency. Thermal strength of the grown crystals has been studied using thermogravimetric (TGA) and differential thermal analysis (DTA). Addition of urea slightly improve the melting point of the crystals.