The annealing effect on the structural perfection of Fe-doped LiNbO 3 single crystals has been studied by high-resolution X-ray diffractometry (HRXRD), X-ray topography (XRT) and Fourier transform infrared (FT-IR) spectroscopy. The single crystals, prepared by mixing Li 2 CO 3 and Nb 2 O 5 powders in the molar ratio 48.6:51.4 with 0.05 mol% of iron at 1415 (1) K, were grown by the Czochralski (CZ) method along the [001] direction in air and poled during crystal growth by the application of a DC field. Two low-angle (tilt angle $1 arc minute) structural grain boundaries were observed in as-grown specimens. FT-IR spectra revealed that these crystals contain OH À and CO 3 2À ionic defects. Grain boundaries and CO 3 2À ionic defects were successfully removed, while the concentration of OH À ions was considerably reduced by post-growth thermal annealing at elevated temperatures.

2-Imino-4-oxo-l,3-thiazolidine, (L), is prepared 1 by the condensation of monochloroacetic acid with thiourea and subsequent hydrolysis of the product with sodium acetate. 2-Imino-4-oxo-l,3-thiazolidine hydrochloride, (LHC1), is prepared by treating L with 6N HCl. Very good colourless needle-shaped crystals of L and prismatic crystals of are obtained by slow evaporation from the respective aqueous solutions.The infrared spectra of the compounds indicate that a strong absorption at 3 225 cm -1 ascribed to exocyclic NH stretching frequency in L, has shifted to lower region (around 3100 cm -1 ) in LHC1. This suggests that in LHC1 the exocyclic -NH group is protonated.A weak intensity band observed at 3 400 cm -1 with a strong and broad band at 3000 cm -1 in L and LHC1 is due to cyclic NH stretching frequency. The appearance of NH stretching frequency, at lower region is attributed to the strong intermolecular hydrogen bonding present in the compounds.Single-crystal rotation and Weissenberg photographs were taken using CuKot radiation, down a axis for L and down a and c axes for LHC1. The crystal data for both the compounds are given in Table 1. LHC1, and (L) (LHC1)

The crystal structure of 2-imino-4-oxo-1,3-thiazolidine hydrochloride C

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