Contemporary studies on growth and characterization of bis (thiourea) strontium chloride-A potential optoelectronic NLO material

Single crystals of pure bis (thiourea) strontium chloride (BTSC) have been grown by slow evaporation method. The solubility and meta-stable zone width of the crystals have been found to have direct relation with temperature. Orthorhombic structure and Pna21 space group of the crystals have been identified using single crystal X-ray diffraction. The purity and stoichiometry of the compound have been established by elemental analysis. Step growth pattern of the crystal has been suggested by etching studies. Seventy-seven percent transmittance measured by the ultra violet transmittance studies and a band gap of 4.7 eV indicated the required optical transparency. The strontium coordination with thiourea through sulfur in BTSC has been ascertained by Fourier Transform Infrared spectral studies. Thermal analysis showed the purity and thermal stability. The values of hardness number, elastic stiffness constant, Meyer's Index, minimum level of indentation load, load-dependent constant and corrected hardness obtained from Vicker's hardness test clearly showed that the BTSC crystal has good mechanical stability. Second Harmonic Generation (SHG) efficiency of BTSC has been calculated to be 1.54 times as that of KDP and the former's phase matching nature has been confirmed by the Kurtz method. Photoconductivity measurements indicated the negative photoconductivity nature. The low birefringence value calculated from birefringence patterns attested the suitability of the crystal to be used in harmonic generation devices. The dielectric constant and the dielectric loss decreased as the frequency of applied field increased. Thus, the suitability of BTSC as a potential candidate for various optoelectronic and laser applications has been established.