Sodium metavanadate (NaV03) has been reported earlier to exhibit ferroelectric behaviour below 380 "C, but unlike many other known ferroelectrics it does not show a very strong dielectric anomaly, indicating that the structural change during the ferroelectric phase transition may be only a slight modification of the paraelectric phase. This is in conformity with the x-ray data at room temperature, which could he refined to the same R value either in space group C2ic or Cc. Further, it is known that NaVO, occurs also in another polymorphic modification (&form), the structure of which has not been established. Raman spectroscopic studies of single crystals of the a-form of NaV03 have been carried out and a crystalline powder of the j3-form has been made. The Raman spectra have been interpreted in terms of the linear VO; chains formed by VO, tetrahedra sharing two corners with each other. The temperature variation of the intensity and width of the Raman lines through the phase transition has been measured and the observed LO-TO splitting in the room temperature phase confirm the Cc ferroelectric space group.

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Raman spectrum of Tris-sarcosine Calcium chloride has been recorded both in the para and ferroelectric phases using Iz = 2537 A of mercury as exciting radiation. The infrared absorption spectrum has been recorded both above and below the Curie temperature, in the region 400 to 4000 cm-l. From the observed splitting of the infrared bands it is concluded that the second order ferroelectric phase transition at 127K is due to a dynamical ordering of sarcosine molecules which exist in zwitteron configuration. Raman spectrum shows eight lattice lines which do not exhibit any anomaly as the crystal undergoes phase transition. Raman Spectroscopy 1 (1973) 499-505. All Rights Reserved Copyright 0 1973 by D. Reidel Publishing Company, Dordrechi-Holland 8J w Journal of

LiNbO3 crystals were grown by Czochralski pulling method. By suitably optimizing the after-heater configuration a crystal to crucible diamter ratio of 64% was achieved. The boules were poled at high temperature for obtaining single domain crystals. Variation of microhardness with applied load was evaluated. Hardness studies on different domains reveled that the negetive domains have higher microhardness than the positive ones.

The Raman spectrum of strontium titanate has been recorded using ~ 4358 of mercury as exciter. The observed spectrum consists of 7 Raman lines, one of which is of low frequency, as expected from the recent theory of Cochran. 6 of these Raman lines have been interpreted as the first order spectrum arising from a small deviation of the cubic strontium titanate from its idealized symmetry. It has been shown that one normal mode of SrTiO a neglected by J.T. LAST, will be really active in infrared absorption in the region of 440 cm -1 and that it has to be taken into account in the interpretation of the infrared spectra of titanates. The four vibrational modes of the unit cell of SrTiO a correspond to frequencies of 90, 335, 441 and 620 cm 1 observed in Raman effect. The large width of the Raman lines and the additional lines at 256 cm ~ and 726 cm -1 have been attributed to a splitting of the longitudinal and transverse optical modes. With the observed frequencies it has been found possible to account for in a satisfactory manner the specific heat of SrTiO a in the range 54.84 ~ IZ to t800 ~ K.