Influence of urea doping on optical, thermal, mechanical and electrical properties of l-arginine phosphate monohydrate crystals for NLO applications

In the present investigation, the influence of urea doping on the optical, structural, thermal, mechanical and dielectric properties of l-arginine phosphate monohydrate (LAP) crystal were investigated. Pure and doped LAP crystals were grown from aqueous solution by evaporating solvent at a constant temperature. The presence of dopant was confirmed qualitatively by FT-IR spectroscopy. Powder X-ray diffraction study reveals slight modification in lattice parameters of doped crystal. Ultraviolet–visible–near infrared transmission study reveals increase in optical transparency and band gap of doped crystals with doping concentration. Other optical parameters such as refractive index, extinction coefficient, reflectance, optical and electrical conductivity of pure and doped crystals were evaluated from transmission spectrum only. Noticeable enhancement in second harmonic generation efficiency (1.67 times more) has been observed for 1 mol percent urea doped LAP crystal as compare to pure one. Doped LAP crystals show higher mechanical and thermal stabilities than pure LAP crystal. Electrical properties like as dielectric constant, dielectric loss, ac conductivity and activation energy were also studied.