Optical, piezoelectric and mechanical properties of xylenol orange doped ADP single crystals for NLO applications

Single crystals of pure and xylenol orange (XO; C31H32N2O13S) dye doped (0.01, 0.05 and 0.1 mol%) ammonium dihydrogen phosphate (ADP; NH4H2PO4) were grown by slow evaporation method with the vision to improve the properties of pure ammonium dihydrogen phosphate crystal. The theoretical morphology of the grown crystals was drawn using Bravais–Friedel–Donnay–Harker (BFDH) law. The selective nature of xylenol orange dye to selectively stain the particular growth sectors of ADP crystal was studied. The structural analysis of as grown crystals was carried out using powder XRD study. The identification of the functional groups present in the ADP material was done using Fourier transform infrared (FTIR) spectroscopy. The linear optical study on pure and dye doped crystals was carried out using UV–vis–NIR spectroscopy. The optical band gap, extinction coefficient, refractive index and optical conductivity were calculated using the transmittance spectra for all the samples. In photoluminescence studies, the blue emission intensity got quenched and an orange emission at 597 nm was seen as a result of XO doping. The thermal stability and decomposition temperature of ADP crystal were found to decrease as an effect of dye doping. The piezoelectric charge coefficient, SHG conversion efficiency, mechanical strength and wettability were also enhanced as a result of XO dye doping. Keywords: Nonlinear optical materials, Dye-doped crystals, Optical properties, Piezoelectricity, Mechanical properties