Raman spectroscopic studies on sodium metavanadate

Abstract

Abstract Sodium metavanadate (NaVO 3 ) 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 be refined to the same R value either in space group C2/c or Cc. Further, it is known that NaVO 3 occurs also in another polymorphic modification (β‐form), the structure of which has not been established. Raman spectroscopic studies of single crystals of the α‐form of NaVO 3 have been carried out and a crystalline powder of the β‐form has been made. The Raman spectra have been interpreted in terms of the linear VO chains formed by VO 4 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 Ce ferroelectric space group.