Journal ArticleDOI
An i.r. study of the phases of lithium ammonium sulphate
S. Alam,J.P. Srivastava +1 more
TLDR
In this paper, the i.r. spectra of lithium ammonium sulphate have been measured at 463, 300, 170 and 30 K covering all the phases of its structure.About:
This article is published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.The article was published on 1981-01-01. It has received 9 citations till now. The article focuses on the topics: Phase (matter) & Lithium.read more
Citations
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Journal ArticleDOI
A Raman study of the high temperature phase transition in lithium ammonium sulphate
TL;DR: In this article, the temperature dependence of the Raman scattering from LiNH4SO4 has been studied to investigate the phase transition at 459.5 K, which is found to be of second-order type.
Journal ArticleDOI
FIR studies of α and β polymorphs of LiNH4SO4 single crystals
TL;DR: In this paper, the authors studied the differences in the extenal vibrations of the two polymorphs, and the α → β polymorphous transformation, and showed that the α polymorph undergoes an irreversible transformation to the β modification (space group P c 2 1 n) exhibiting a ferroelastic-paraelastic phase transition at about 284 K and an ferroelectric-paraelectric transition at T c ≈ 460 K.
Journal ArticleDOI
Raman spectra of a LiN(HxD1-x)4SO4 mixed crystal
TL;DR: In this paper, the Raman spectra of a deuterated lithium ammonium sulphate single crystal were studied at 77 to 493 K. The results showed that the I-II-III phase transitions are bonded essentially with the dynamics of Li-SO4 framework; however, no clear-cut conclusions can be drawn about the role of the NH4-sublattice in these phase transitions.
Journal ArticleDOI
Ferroic phase transitions in β-LiNH4SO4
TL;DR: In this article, the authors review the results of experimental and theoretical studies of ferroic phase transitions in β-LiNH4SO4 and its deuterated analogue, and focus on the influence of the order of phase transitions on the pattern of the ferroelectric and ferroelastic domain structure, and also the role played by the dynamics of molecular groups in the mechanism of transitions.
Journal ArticleDOI
Raman spectra and improper ferroelastic phase transition in single crystal
TL;DR: Polarized Raman spectra of lithium ammonium sulphate (LAS) single crystals in the temperature range 40-290 K have been studied and compared with the available data.
References
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Journal ArticleDOI
Motions of Molecules in Condensed Systems: I. Selection Rules, Relative Intensities, and Orientation Effects for Raman and Infra‐Red Spectra
TL;DR: In this paper, the distribution of point symmetries within space groups and the population of the unit cell were used to derive selection rules for Raman and infra-red spectra of crystals.
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The Vibrational Spectra of Molecules and Complex Ions in Crystals III. Ammonium Chloride and Deutero‐Ammonium Chloride
E. L. Wagner,D. F. Hornig +1 more
TL;DR: In this paper, the infra-red spectra of thin non-scattering films of NH4Cl and ND4Cl were obtained at 28°, −78° and −190°C.
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The Vibrational Spectra of Molecules and Complex Ions in Crystals. I. General Theory
TL;DR: In this paper, it was shown that if a crystal is approximated as a harmonic oscillator, only a very small number of vibrational modes may be active in the infra-red or Raman spectra.
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Infrared Spectra of Molecules with Hydrogen Bonds
S. Bratož,D. Hadži +1 more
TL;DR: In this paper, it was shown that the broad hydrogen stretching bands associated with strong hydrogen bonds are not single bands, but groups of bands which are very sensitive to intermolecular influences.
Journal ArticleDOI
Ferroelectricity in NH 4 IO 3
Toshiharu Mitsui,Tateki Oka,Yoshihiro Shiroishi,Masaaki Takashige,Katsunori Iio,Shozo Sawada +5 more
TL;DR: In this article, it has been found that in NH 4 LiSO 4 another transition point 186.5°C exists in addition to the already known one 10°C and this substance is ferroelectric between these two transition points.