Non-linear optical (NLO) single crystals of L-valine l-valinium orthophosphate (LVP) and L-valine l-valinium nitrate (LVN) were grown by slow evaporation solution growth method using water as the solvent at room temperature. Purity of the crystals was increased by the method of recrystallization. The cell parameters of LVP and LVN were determined using single crystal X-ray diffraction technique. The grown crystals were characterized by measuring their thermal, optical and mechanical properties

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... y Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TGA), Powder Second Harmonic Generation (SHG) efficiency, FTIR, UV-VIS NIR, damage threshold and microhardness measurements. The dielectric constant and dielectric loss of the crystals have been studied as a function of frequency at room temperature. Our studies showed that L-valine inorganic acids emerged as most promising NLO materials having SHG efficiency, mechanical and thermal stability greater than other semi-organic NLO materials. 1 Introduction Non-linear optics (NLO) is an innovative area of research and development which plays a key role in the field of optoelectronics and photonics 1. The apparent development of semi-organic materials, where the organic ligand is ionically bonded with inorganic host refined the search of new materials with high optical nonlinearities which is an important area due to their optical applications such as optical communication, optical computing, optical information processing, optical disk data storage, laser fusion reaction, laser remote sensing, colour display, medical diagnostics, etc. 2. Nonlinear optical (NLO) materials play a major role in non-linear optics and in particular they have a great impact on information technology and industrial applications. The new development technique for the fabrication and single crystal growth of nonlinear optical materials has dramatically contributed to this evolution. On account of the large flexibility for molecular design and higher nonlinear optical efficiency, there has been much progress in basic research on organic and semi-organic NLO materials. In this respect, amino acids are interesting materials for NLO applications 3-8. The importance of amino acids for NLO application lies on the fact that almost all amino acids contain an asymmetric carbon atom and crystallize in non-centrosymmetric space group,