Jr. Shi et al., RAMAN-SCATTERING AND X-RAY-DIFFRACTION STUDY OF A PHASE-TRANSITION IN(ND4)(2)TEBR6, Journal of Raman spectroscopy, 27(9), 1996, pp. 691-694
Raman spectra of (ND4)(2)TeBr6 were recorded in the temperature range
5-300 K, A continuous minimum of the Raman shift and a continuous maxi
mum of the linewidth of the A(1g) mode of the TeBr62- octahedron were
observed at T-c = 68 K. Also, the T-2g mode of the TeBr62- octahedron
continuously split into two lines below T-c. X-ray diffraction measure
ments at 10 K indicate that the low-temperature phase has a primitive
tetragonal structure, and an antiferro-rotation of the TeBr62- octahed
ra is associated with the transition. This behaviour indicates a displ
acive phase transition at T-c.