Lattice dynamics calculations and temperature dependence of vibrational modes of ferroelastic Li₂TiGeO₅

Abstract

Raman and polycrystalline IR spectra were obtained for Li2TiGeO5 and the assignment of the observed bands to the respective internal and external phonons has been proposed on the basis of lattice dynamics calculations. Temperature dependences of Raman- and IR-active phonons are also reported to probe the paraelastic–ferroelastic phase transition that takes place at 233.5 K. This study shows that the phase transition is continuous and that this phase transition leads to significant distortion of the unit cell.

Synthesis and Optical Properties of Pure and Doped M2TiGeO5(M = Li and Na) Ceramics

“…Since the discovery of ferroelasticity in this material, LTGO has been intensively studied using various experimental methods. The ferroelastic character of the phase transition in LTGO was confirmed by studies of the electric permittivity, the thermal, the optical and the elastic properties [8][9][10].…”

Na2TiGeO5: Crystal structure stability at low temperature and high pressure

“…[11] that the transition is accompanied with a symmetry transformation to an orthorhombic structure with space group Pmmn. Temperature-dependent evolution of Brillouin scattering and lattice dynamics calculations based on results of IR and Raman spectroscopy are indicating a transition of continuous character [12].…”

Synthesis and structural study of a new group of trigermanates, CaRE2Ge3O10(RE = La–Yb)

“…However, the bands associated with ν s IJGeOGe) are shifted to 541 cm −1 and 536 cm −1 in the spectra of CaLa 2 Ge 3 O 10 , and are represented as weak infrared bands and Raman lines, respectively (Fig. 46,51,55,57 Vibrations in the region of lattice modes. Only weak shoulders at 590 cm −1 (infrared spectrum) and~570 cm −1 (Raman) remain in the spectra of CaLa 2 Ge 3 O 10 near those positions of ν s IJGeOGe) from CaRE 2 Ge 3 O 10 (RE = Nd, Gd, Tb, Y).…”

“…The bending vibrations of the terminal Ge-O bonds reveal themselves more distinctly in the infrared spectra than in the Raman ones that is typical and also stands in line with the earlier studies on Yb 2 CuGe 4 O 12 , Li 2 TiGeO 5 , Sr 2 ZnGe 2 O 7 and other pyrogermanates, and proves the strong vibrational mixing expected below ~550 cm −1 . 46,51,55,57 Vibrations in the region of lattice modes. A part of the region of lattice modes is out of our infrared instrument range.…”