Sodium metavanadate (NaVO3) 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 NaVO3 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 NaVO3 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 VO3− chains formed by VO4 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.

Raman spectroscopic studies on sodium metavanadate

Activating abnormal capacity in stoichiometric NaVO3 as cathode material for sodium-ion battery

High temperature and high pressure Raman study of LiVO3

Structural Disorder and Ionic Conductivity in LiVO3: A Neutron Powder Diffraction Study from 340 to 890 K

In situ high-pressure infrared spectra of α-NaVO3

The crystal structure of ferroelectric sodium meta vanadate, NaVO3 has been solved using three dimensional X-ray data and refined to an R-value of 0.077 for 375 observed reflections. The crystal belongs to the monoclinic system with space group Cc and with unit cell dimensions a = 10.494 (9) A, b = 9.434 (7) A, c = 5.863 (6) A and β = 108° 48' in the room temperature ferroelectric phase. The unit cell dimensions in the high temperature paraelectric phase (above 380°C) are a = 10.595 (15) A, b = 9.671 (10) A, c = 5.926 (8) A and β = 108° 45' with space group C2/c. The crystal structure may be viewed as consisting of alternate channels of sodium polyhedra and VO4 tetrahedra.

B. Swaminatha Reddy

Papers

Crystal structure of ferroelectric sodium meta vanadate, NaVO3