Crystal growth, A.C. electrical and nonlinear optical studies of pure and dl-methionine doped ammonium dihydrogen phosphate single crystals

The pure and 0.1 wt% dl-methionine doped ADP crystals are grown using slow solvent evaporation technique at room temperature. The powder XRD study shows single phase nature of both grown crystals with tetragonal structural symmetry. The UV–Vis transmittance spectroscopy shows improvement in optical transmittance, energy band, and low refractive index of doped ADP crystal compare to pure ADP crystal. The Wemple–DiDomenico single oscillator model is found to be appropriate for the refractive index dispersion below the energy band edge of ADP crystal. The Nyquist plots of pure and doped ADP crystals represent presence of grain and grain boundary. The Jonscher’s powder law is successfully applied to the conductivity phenomena in pure and doped ADP crystals. The complex modulus spectroscopy helps to discriminate the grain and grain boundary in grown crystals clearly. The Non-Debye type relaxation is observed in both crystals. The nonlinear optical properties such as second harmonic generation efficiency and third order susceptibility are improved on doping the dl-methionine in ADP crystal.