In situ Raman investigation of the phase transition of NaVO(2)F(2) under variable temperature conditions

In this study, the phase transition of NaVO(2)F(2) was measured at different temperatures via in situ Raman spectroscopy. The NaVO(2)F(2) compounds were synthesized by a hydrothermal method and were identified to be monoclinic with the P2(1)/c space group at room temperature by XRD. Accordingly, the variations of Raman shifts and intensities of the characteristic peaks for NaVO(2)F(2) associated with temperature were obtained and investigated. It was confirmed that NaVO(2)F(2) had three types of phase transitions, which occurred in the temperature region from 78 K to 573 K. Further, the results indicate that transition from a low-temperature phase (I) to another low-temperature phase (II), low-temperature phase (II) to P2(1)/c phase and P2(1)/c phase to P2(1)/m phase occurred near the three temperature points of 93 K, 233 K, and 453 K, respectively, during the heating process. Therefore, a novel characterization method was provided for further research on the phase transition theory and performance of vanadate compounds.