Doping effect of urea on growth, spectral, thermal, mechanical, electrical, nonlinear and optical studies of Sr(HCOO)2·2H2O crystal: enhanced third-order NLO properties with a high laser-induced damage threshold

Abstract

Pure and urea doped (with 3 different concentrations, viz. 0.005, 0.05, and 0.1 M) strontium formate dihydrate (SFD, Sr(HCOO)2·2H2O) single crystals were grown from aqueous solutions by using slow solvent evaporation technique. In order to understand the effect of urea doping on the structural, chemical, thermal, morphological, optical properties of SFD crystals, the grown crystals were characterized by carrying out CHN analysis, powder X-ray diffraction, high resolution X-ray diffraction, Fourier transform infrared spectral, thermogravimetric, UV–Vis–NIR spectral, photoluminescence spectral, second harmonic generation efficiency, and Z-scan measurements. The results obtained indicate that the urea molecule have entered into the SFD crystal matrix and has improved the crystallinity. Also, the results indicate that urea doping significantly tunes the optical and thermal properties without significantly distorting the crystal structure of SFD crystal. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser as a source in single-shot mode (1064 nm, 10 Hz, 420 mJ). The result of laser damage threshold (LDT) energy indicates that grown title crystal has excellent resistance to laser radiation than those of some known inorganic NLO materials. Its third-order nonlinear optical properties were investigated by Z-scan technique and proved that the grown crystal possesses two-photon absorptions (TPA) and the self-defocusing effect.