Microhardness and SHG efficiency of pure and picric acid-added KDP crystals

Pure and picric acid-added KDP (potassium dihydrogen phosphate) crystals are grown by slow evaporation technique from aqueous solution. Unit cell parameters for pure and doped KDP crystals were measured from single-crystal X-ray diffraction studies. Vickers and Knoop microhardness studies were carried out on the grown crystals over a load range of 0.1 to 0.5 N. The microhardness decreases with load P, i.e., normal indentation size effect (ISE), and from Meyers index it is shown that grown crystals falls in to hard material category. Mechanical properties, such as Young’s modulus, yield strength, elastic stiffness constant, were calculated for pure and doped KDP crystals. Hardness anisotropy has been observed in accordance with the orientation of the crystal. Etching studies were carried out using aqueous solution as an etchant. Improved second-harmonic generation efficiency is observed for doped KDP crystals in comparison to pure KDP crystals.