Brillouin scattering study of ferroelectric NH4LiSO4: Relaxation time and anomalous temperature dependence of elastic constants

Hirotsu, Shunsuke

doi:10.1080/00150198308208235

Cited by 12 publications

(3 citation statements)

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“…The elastic constants of LAS at room temperature have been measured by earlier workers using ultrasonic 3 and Brillouin-scattering [9][10][11] techniques. The temperature variation of selected elastic constants near the 460 K ferroelectric phase transition has been determined by ultrasonic 12 and Brillouin-scattering 13,14 techniques. Also, clear evidence for the ferroelastic transition at 285 K has been obtained in the experimental results on the temperature variation of the elastic constants using Brillouin-scattering technique.…”

Section: Introductionmentioning

confidence: 99%

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Godfrey

Philip

1996

Phys. Rev. B

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A detailed ultrasonic study of the elastic properties of lithium ammonium sulfate ͑LiNH 4 SO 4 ͒ or LAS has been carried out below room temperature. The elastic constants of LAS at room temperature are reported. The discrepancy present in earlier elastic constant data associated with the different choice of axes for this orthorhombic system are clarified. The results of the temperature variation study down to 220 K confirm the ferroelastic phase transition at 285 K and establish a thermal hysteresis of about 2.5 K between the cooling and heating cycles. Results of the investigation on the suspected weak phase transition at 256 K suggest that this transition occurs at 242 K on cooling and at 256 K on heating, thus having a thermal hysteresis of about 14 K. However, since the observed elastic anomaly for this transition is very small, the nature of this transition still remains unclear. ͓S0163-1829͑96͒01046-6͔

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Section: Introductionmentioning

confidence: 99%

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Godfrey

Philip

1996

Phys. Rev. B

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“…Recently the temperature behaviour of the elastic constants around the phase transition at 460 K has been carefully measured by Brillouin scattering (BS) (Hirotsu 1983, Luspin et a1 1984, 1985 and ultrasonic (U) (Wyslouzil et af 1986) techniques. The agreement of the results is quite good for the longitudinal constants CI1, C22 and C33 and for the shear constants CU and C, .…”

Section: Introductionmentioning

confidence: 99%

Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

Masuyama¹,

Mizutani

Nagai

2005

Jpn. J. Appl. Phys.

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Above 460 K the temperature behaviours of the elastic constants C, , of NH4LiS04 as measured by the Brillouin scattering and ultrasonic techniques are different. As measured by ultrasound, C, , exhibits a behaviour typical for an elastic phase transition although the relevant phase transition is ferroelectric and certainly not ferro-elastic. Here we argue that in the para-electric phase above 460 K the two soft relaxational modes of symmetry B3" and BZg exist. Only the B3" mode causes the phase transition to the ferroelectric phase. The B2% mode couples to the low-frequency shear mode of the same symmetry producing the observed temperature behaviour of the C,elasticconstant. This behaviourchangeswith the frequency used by a given experimental technique and depends on the temperature variation of the relaxation time of the BZg mode.

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“…To date all the papers concerned with Brillouin studies of LAS (Hirotsu et a1 1981, Hirotsu 1983, Yamamoto et a1 1983, Luspin et a1 1985, Schranz et a1 1987b have been devoted to the high-temperature ferroelectricphase transition at 460 K. Since this crystal exhibits extremely weak scattering at room temperature, there are no direct results for the purely transverse modes.…”

Section: Introductionmentioning

confidence: 99%

On the ferroelastic phase transition of LiNH₄SO₄: a Brillouin scattering study and theoretical modelling

Mróz

Tuszyński

Kiefte

et al. 1989

J. Phys.: Condens. Matter

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Brillouin spectroscopywas used to study the elastic properties of LiNH,S04 in the vicinity of the ferroelastic first-order transition occurring at approximately 285 K. Eleven acoustic modes were observed in the temperature range from 273 to 293 K . Their sound velocities and the temperature dependences of the corresponding elastic constants were calculated from the measured frequency shifts. The measured elastic constants exhibited step-like dicontinuities at the transition temperature and were interpreted using a symmetryadapted Landau free-energy expansion. The order parameter for the ferroelectric phase transition at 460 K was chosen to be an infrared-active soft mode; while for the ferroelastic phase transition at 285 K, a two-component soft mode from the X point of the Brillouin zone was chosen. Both of these order parameters are coupled to polarisation and strains.

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Brillouin scattering study of ferroelectric NH4LiSO4: Relaxation time and anomalous temperature dependence of elastic constants

Cited by 12 publications

References 3 publications

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

On the ferroelastic phase transition of LiNH₄SO₄: a Brillouin scattering study and theoretical modelling

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Brillouin scattering study of ferroelectric NH4LiSO4: Relaxation time and anomalous temperature dependence of elastic constants

Cited by 12 publications

References 3 publications

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Phase transitions in lithium ammonium sulfate below room temperature: An ultrasonic study

Directional Trimming of Radiated Ultrasonic Beam Using Decentered Annular Transducer Array

On the ferroelastic phase transition of LiNH4SO4: a Brillouin scattering study and theoretical modelling

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On the ferroelastic phase transition of LiNH₄SO₄: a Brillouin scattering study and theoretical modelling