Synthesis and characterization of semi-organic nonlinear optical material: Sodium para-nitrophenolate para-nitrophenol dihydrate

Single crystal of sodium para-nitrophenolate para-nitrophenol dihydrate (SPPD) was grown using slow evaporation solution growth technique with the crystal dimensions of 17 mm × 11 mm × 6 mm. The structure of the SPPD crystal was examined by X-ray diffraction analysis and the functional groups, hydrogen bonding interactions were identified using FT-IR and FT-Raman spectra. The UV–vis-NIR absorption spectrum revealed that the UV lower cut-off wavelength was 260 nm and the optical band gap of the crystal was 4.76 eV. The material was thermally stable up to 128 °C as determined by the TG-DTA curves. The mechanical behavior of the grown crystal was studied using Vickers microhardness. Dielectric constant and dielectric loss were also measured as a function of frequency between 5 Hz and 5 MHz and temperature between 40 and 100 °C, respectively. The second-harmonic generation efficiency was found to be five times greater than that of KDP. The third-order nonlinear parameters such as nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third-order susceptibility |χ(3)||χ(3)| were calculated using Z-scan technique.