Synthesis, growth, optical and mechanical studies of ferroelectric urea-oxalic acid single crystals

Abstract

A single crystal of urea oxalic acid was grown by slow evaporation method. The lattice parameters are a=5.13Å, b=12.48Å, c=7.07Å, β=98.13° with V=448.5Å3 which belongs to monoclinic system with space group P21/c obtained from single crystal X-ray diffraction analysis. UV–visible spectrum was recorded from the wavelength region of 200–800nm and its cutoff wavelength was found to be 270nm. Optical energy band gap of 4.57eV was determined using Tau's plot relation. Fourier transform infrared vibrational spectrum confirmed the presence of N–H asymmetric stretching which occurs at 3444cm−1 and 1853cm−1 arising due to the amide C=O symmetric stretching. The emission was observed at 364nm from the photoluminescence spectrum. The mechanical stability of the grown crystal was estimated by Vickers microhardness studies and it is evident that the grown crystal belongs to soft material category. Hardness related parameters such as elastic stiffness constant, fracture mechanics, brittleness index and yield strength were also evaluated. The dielectric constant and dielectric loss of the grown crystal were carried out as a function of frequency for different temperatures.