Investigations on surface and mechanical properties of bis-thiourea cadmium iodide – A non-linear optical crystal

Abstract

The semi-organic non-linear optical crystals of bis-thiourea cadmium iodide (BTCI) were grown from slow evaporation of their aqueous solutions. The grown crystals were confirmed with XRD, FTIR, and DSC analysis. The as-grown (010) crystal faces reveal growth striations. The structural perfection was assessed by the wet chemical etching method; acetic acid and formic acid are the best etchants to reveal dislocations. The strength and deformation characteristics of the crystals were assessed through laser damage tolerance, Vickers, and Knoop hardness measurements. The change in hardness is approximately 26% for every 40–45° shift in the orientation of the crystal, indicating anisotropy in hardness. The work hardening index calculated from Meyer's plot helps in distinguishing the indentation size effect. The yield strength and Young's modulus calculated using the standard relations indicate that the crystal is suitable for desired applications.