Structural Chemistry & Crystallography Communication

Tri glycine sulphate (NH2CH2COOH)3.(H2SO4) (TGS) is a ferroelectric and pyroelectric crystal which is mainly used for infrared detector applications. The b axis of TGS is the ferroelectric axis (axis of spontaneous polarization) and along this axis it exhibits maximum pyroelectric co­efficient of ~ 3 × 10-2 μC cm-2 K-1 at room temperature [1]. Due to this reason the (010) face assumes importance in the morphology of TGS crystal. The work described in the present report is an attempt to study the evolution of the morphology of TGS crystal in general and (010) face area relative to other faces in particular and also to characterize the grown crystal for its phase and optical homogeneity using X-ray diffraction and optical interfer­ometric techniques. Also to study the effect of dopping of TGS with potassium succinate. TGS is known to un­dergo a second order (order-disorder type) continuous phase transition at the Curie temperature (Tc) of 49°C. Below this temperature the crystal exhibits ferroelectric phase whereas above it the crystal gets transformed to the paraelectric phase [2]. It belongs to monoclinic system be­low and above the Curie temperature. It has space group P21 in the ferroelectric phase and cento-symmetric space group P21/m in the paraelectric phase [3]. The lattice pa­rameters of TGS are a=9.41Å, b=12.64 Å, c=5.73 Å and β=110°23’ [4]. Due to its self poling nature it does not re­quire any specific poling when it is cooled from the high temperature phase to the low temperature one. Taking advantage of this characteristic of TGS, and the fact that across the Curie temperature the dipole moments of the domains will behave differently which will influence the growth rate of the (010) polar face, we have attempted to grow TGS crystal . The morphology of TGS crystal in general and (010) face in particular is studied. Also we at­tempted to study doping induced morphological changes of TGS using Potassium Succinate as dopant.