Growth and physical properties of a new crystal for NLO applications: Bisguanidinium hydrogen phosphate monohydrate (G2HP)

Single crystals of nonlinear optical material bisguanidinium hydrogen phosphate monohydrate (G2HP) belonging to non-centrosymmetric space group P4̄21c were successfully grown by the slow evaporation method. G2HP crystals of size 32×3×3 mm3 were obtained in 20 days. Initially, solubility tests were carried out for three solvents such as water, water–methanol, water–ethanol. Among the three solvents, the solubility of G2HP was found to be the highest in water, so crystallization of G2HP was done from its aqueous solution. Morphological analysis reveals that the crystal is rectangular in shape with six developed faces with major face forms along {1 1 1}, {1 2 0} and {−1 1 0} crystallographic axes. As grown, crystals were characterized by X-ray powder diffraction studies, optical transmission spectral studies and laser damage threshold studies. Nonlinear optical (NLO) behavior of G2HP crystal was studied by Kurtz powder. Infrared spectroscopy, thermo gravimetric analysis and differential thermal analysis measurements were performed to study the molecular vibration and thermal behavior of G2HP crystals. Thermal analysis and micro hardness measurements for G2HP crystal were carried out. The chemical etching study was carried out using deionized water with ethanol (1:1) ratio as an etchant.

► Grown crystals are observed to be transparent and colorless with well defined appearance.
► Laser damage energy density for multiple shot was found to be 7.1 GW/cm2.
► TG-DTA studies establish that the compound is stable upto its decomposition point at 130.3 °C.
► SHG efficiency of G2PH is found to be 1.2 times higher than that of KDP crystals.