Raman scattering in lithium ammonium sulphate

Abstract

Polarized Raman spectra of single crystals of lithium ammonium sulphate (LiNH,SO,) have been obtained. Detailed assignments of symmetry were made using selective scattering geometries. Separation of TO and LO components were either observed experimentally or calculated using oblique phonon frequency measurements.

Raman study of LiCsSO4

“…Actually, this has been observed in the case of several Li compounds: LiNH,SO, [9], Li,SO, [lo], LiKSO, [ll], and LiNaSO, [12]. The weak bands around 400 cm-' may be assigned to librational motions of the sulfate ions (SO, -R), considering that this kind of vibration frequency (ern-') Fig.…”

Phase transition studied by7Li nuclear magnetic resonance in LiXSO4(X = K, Rb, Cs and NH4) single crystals

“…The increasing number of studies being performed on the physical properties of LiXSO 4 (X = K, Rb, Cs and NH 4 ) single crystals are largely owing to its excellent optical quality. These crystals have previously been investigated by means of x-ray diffraction [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], Raman spectroscopy [16][17][18][19][20][21][22][23][24][25][26][27][28], EPR [29][30][31][32][33][34][35][36][37][38][39][40][41], NMR [42][43][44][45][46][47][48][49][50]…”

Raman spectra and improper ferroelastic phase transition in single crystal

“…Experimental Raman studies of LAS are numerous, most of them being devoted to detailed assignment of LO-TO components in the room-temperature polar phase [10], to the hightemperature ferroelectric transition [11][12][13] or to the high-pressure transition [14]. However, lattice dynamics in the low-temperature ferroelastic phase of LAS has not been sufficiently well studied and there are only very few papers where some fragmental Raman spectra restricted to the frequency region of external modes were reported [12,15,16].…”