%0 Journal Article
%T Vibrational Spectral Studies of Pure and Doped TGSP Crystals
%A N. Kartheeswari
%A K. Viswanathan
%J Journal of Spectroscopy
%D 2013
%R 10.1155/2013/272069
%X Triglycine sulfate crystals (TGS) are an important class of ferroelectric materials. TGS have attracted many researches because of thier room temperature ferroelectric nature. TGS found wide applications in electronic and optical fields. In present work, pure and ADP-, KDP- (0.2£¿mol) doped TGSP crystals are grown from solution growth method. Grown crystals are subjected to UV-Vis, IR, and Raman spectral studies. Crystal structure of grown crystals is obtained from powder XRD pattern. Ferroelectric nature of grown crystals is tested using homemade Sawyer-Tower circuit. Electrical conductivity measurements are carried out for pure and doped TGSP crystals. 1. Introduction Triglycine sulfate is a ferroelectric material and belongs to the pyroelectric family. It plays a major role in FT-IR instrumentation and infrared detector. It exhibits order-disorder phase transition at the Curie point 49¡ãC. The crystal structure of TGS was reported by Hoshino et al. [1]. The unit cell of TGS contains three types of glycines GI, GII, and GIII. Glycine I is in the form of zwitterion. GII and GIII are two planar glycines. They have protonated carboxyl groups which have taken protons from the sulfuric acid. They form chain-like system with group. The neighbouring chains are connected by groups of adjacent chains and GI group. Such configuration of TGS is regarded as particularly important for the ferroelectric behavior of TGS crystal. The orientation of positively charged NH3 groups determines the direction of spontaneous polarization in TGS. The spontaneous polarization reversal in TGS is due to the proton transfer between glycine and glycinium ions [2]. TGS exhibits order-disorder phase transition at the Curie point. Above Curie temperature, it is in the Paraelectric phase with space group symmetry P21/m and below Curie it is in the ferroelectric phase with space group symmetry P21 with two formula units per unit cell [3]. The unit cell parameters of TGS are .15£¿£¿, £¿£¿, £¿£¿, and [4]. In TGS, majority of domains were found in the form of rod shapped with lenticular cross-sections elongated in the direction perpendicular to -axis [5]. TGS provides rich lattice vibration spectrum below 300£¿cm£¿1 [6]. The main disadvantage of TGS is its lower Curie temperature and easy depolarization by time, electrical, mechanical, and thermal means. Because glycine has no asymmetric carbon and it is optically inactive, it is believed that doping of TGS with an optically active molecule will keep permanent polarization in TGS lattice. There are a large number of researches going on TGS to
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