Structural, mechanical, optical, dielectric and SHG studies of undoped and urea-doped γ-glycine crystals

Single crystals of undoped and urea-doped γ-glycine (gamma-glycine) were grown from aqueous solutions by slow evaporation technique. Morphological changes were noticed in γ-glycine crystals when urea was added as dopant. Single crystal X-ray diffraction (XRD) studies were carried out to find crystal structure and lattice parameters of the grown crystals. UV-Visible transmittance spectra were recorded for the samples to analyze the transparency in visible and near infrared (NIR) region and UV cut-off wavelength observed for the samples to be at 257 nm. Nonlinear optical (NLO) activity of the grown crystals was studied using a Q-switched and pulsed Nd:YAG laser and second harmonic generation (SHG) efficiency was found. Values of work hardening coefficient were determined from microhardness studies and confirmed that the grown crystals belong to the category of soft materials. Measurements on values of dielectric constant, dielectric loss, AC conductivity and activation energy of the samples were carried out to understand the electrical phenomena that are taking place in pure and urea-doped γ-glycine crystals.