Growth and characterization of new nonlinear optical thiourea L-alanine acetate single crystal

A new nonlinear optical material, thiourea L-alanine acetate (TLAA), has been synthesized. Single crystals of TLAA have been grown successfully by slow evaporation method. The grown crystals have been subjected to X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), second harmonic generation (SHG), ultraviolet-visible spectral analyses, dielectric studies, etc. The structure analysis reveals that it belongs to the orthorhombic crystallographic system, space group P2(1)2(1)2(1), with cell parameters: a = 6.031 angstrom, b = 12.32 angstrom, c = 5.78 angstrom, alpha = beta = gamma = 90 degrees with a cell volume V = 429.47 angstrom(3). The vibrational frequencies of various functional groups in the crystals have been derived from FTIR spectrum. Optical transparency of the grown crystals was investigated by UV-Vis-NIR spectrum. The lower optical cutoff wavelength for this crystal was observed at 300 nm and energy band gap is 3.74 eV. Thermogravimetric (TG) and differential scanning calorimetric (DSC) analyses have been performed to show that TLAA is thermally stable up to 206.22 degrees C. Capacitance and dielectric loss measurements were carried out and the dielectric constant was calculated at room temperature in the frequency range 100Hz-2 MHz. The dielectric constant has a high value of 190.92 at 100 Hz and decreases to 54.69 at 2 MHz. (C) 2008 Elsevier B.V. All rights reserved.