Elastic Constants and Thermal Expansion of CsPbCl<sub>3</sub>

Hirotsu, Shunsuke; Suzuki, T.

doi:10.1143/jpsj.44.1604

Cited by 40 publications

(23 citation statements)

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“…An elastic anomaly was also found in CsPbC^ (Ref. 16), where the soft mode was highly overdamped. Thus an elastic anomaly accompanied by a phase transition seems to be a common characteristic of crystals of which the soft mode is said to be highly overdamped.…”

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confidence: 65%

Elastic Anomaly and Phase Transition of BaTiO3

Ishidate

Sasaki

1989

Phys. Rev. Lett.

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The acoustic-phonon velocities of a single crystal of BaTi03 have been measured as a function of pressure up to 8 GPa, including the transition pressure p c =2.35 GPa, by means of Brillouin scattering technique. Only one elastic eigenmode shows an anomalous decrease on approaching p c and the elastic anisotropy increases. The elastic anomaly of cubic BaTiC>3 is interpreted well by introducing a new tensorial order parameter which describes the anisotropy. The cubic-to-tetragonal phase transition in BaTiC>3 is shown to be triggered by the fluctuation of the anisotropy, not the polarization itself.PACS numbers: 77.80.Bh, 62.50.+p, 62.65.+k, 78.35,+c Studies on the cubic-to-tetragonal phase transition in BaTiC>3 have been extensively done, 1 ' 2 using a variety of experimental methods. The result of an infrared measurement by Luspin, Servoin, and Gervais showed that the frequency co s of the soft phonon mode varies from 1350 to 520 K as G)}azT-T c , but becomes independent of temperature below 520 K to T c , 3 and suggested the existence of a crossover from displacive to order-disorder type of transition. 4 The recent results of hyper-Ramanscattering measurements, which were done independently by Inoue and Akimoto 5 and by Vogt, Sanjurju, and Rossbroich, 6 were in conflict with each other as to the interpretation of the phase transition, i.e., whether the mechanism of the phase transition is of the orderdisorder type or of the displacive type. Thus the controversy on the mechanism of the phase transition is still unresolved.A measurement of inelastic neutron scattering showed the existence of a strong anisotropy in the spectra near the phase transition. 7 The anisotropy seems to be related to the elastic anisotropy. Although the elastic anomaly of BaTiC>3 was observed in the cubic phase near the phase transition, 8 the contribution of the elastic anisotropy to the phase transition was not elucidated since the experiments on the elastic properties were partly performed within the limited region close to the phase transition. Thus no systematic study of the elastic properties of BaTiC>3 has been hitherto performed in relation to the elastic anisotropy. If the anisotropy plays an important role in the phase transition, the studies on the elastic properties will give important information on the mechanism of the phase transition since the anisotropic fluctuation should be of relaxational type.By means of the Brillouin scattering technique in combination with a diamond anvil cell, we have performed the first systematic study of the elastic properties of BaTiOs for a wide region including the phase-transition point, as a function of pressure at room temperature. We have found that the elastic anisotropy increases anomalously on approaching the phase transition. The purpose of this paper is to give new insight into the phase-transition mechanism of BaTiC>3 on the basis of the elastic anomaly accompanying the phase transition.The 6-cut plates were prepared from a melt-grown BaTiOs single crystal (NEC Co. Ltd.) which has ...

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confidence: 65%

Elastic Anomaly and Phase Transition of BaTiO3

Ishidate

Sasaki

1989

Phys. Rev. Lett.

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“…In a subsequent analysis, Liu et al (1991) have reinterpreted their diffraction data to indicate that the high temperature phase is actually a pseudotetragonal modification of an orthorhombic perovskite structure. On the basis of additional weak reflections not allowed by Pbnm symmetry, these authors suggest a Cmcm (DI~) space group for this high temperature phase, similar to that displayed by CsSrC13 between 90 and 102~ (Prokert 1981), and CsPbC13 perovskite from 37-42~ C (Fujii et al 1974;Hirotsu and Suzuki 1978). Although symmetry constraints require that the Pbnm-to-Cmcm transition must necessarily be first order, no resolvable discontinuities were observed in the lattice parameters at the transition temperature, although a small increase (13%) in the thermal expansion coefficient was noted.…”

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confidence: 89%

Raman scattering study of the high-temperature vibrational properties and stability of CaGeO3 perovskite

1991

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Abstract. The vibrational properties of metastable CaGeO3 perovskite are investigated as a function of temperature using Raman scattering. Mode-assignments are derived from polarized spectra of optically oriented single crystals. Neither symmetry-breaking structural transformations nor soft-mode behavior is revealed in the Raman spectra between room temperature and 650 ~ C. Only a small decrease in the local static octahedral tilt angles can be inferred from the Raman data over this temperature range. A Landau extrapolation of the lowest frequency Ag modes suggests that these modes become critical near 2000 ~ C, a temperature that is above the extrapolated zero pressure melting point.

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“…(eg. CsPbCla, Hirotsu and Suzuki 1978;CsSrCla, Midorikawa et al 1976;RbCdFa and T1CdF3, Rousseau et al 1975;SrTiO3, Sato etal. 1985 and SrZrO3, Carlson i967).…”

Section: = Cos-1 (A/c) Data Analysis Indicates That Octahedralmentioning

confidence: 99%

Thermal expansion of SrZrO3 and BaZrO3 perovskites

Zhao

Weidner

1991

Phys Chem Minerals

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Abstract. High-temperature X-ray diffraction studies of SrZrO 3 and BaZrO 3 perovskites have been carried out to 1200 ~ C. The diffraction patterns are analyzed with Rietveld method so as to refine the unit cell dimensions. The volumetric thermal expansion coefficient are observed to be 2.98.10-SK -1 for orthorhombic Pbnm phase, 3.24.10-5K -1 for orthorhombic Cmcm phase, 3.75.10-SK -~ for tetragonal I4/mcm phase of SrZrO3 perovskite, and 2.06* 10-SK -1 for cubic Pm3m phase of BaZrO3 perovskite, respectively. The linear thermal expansion coefficients of SrZrO 3 perovskite show considerable anisotropy of e, > ec> eb for orthorhombic Pbnm phase, which reflect the decrease of distortion of the perovskite. It is demonstrated that thermal expansion of the centrosymmetrically distorted ABX 3 perovskite can be empirically expressed as a combination of the changes of [B-X] bond length and tilting angle of BX6 octahedral framework. The octahedral tilting is considered to be the primary order parameter for the ferroelastic type of structural phase transitions in perovskite. Thermodynamically, the tilting induced volume change denotes the "excess volume" and the corresponding thermal expansion represents the "excess thermal expansion" for the lower symmetry phase with respect to its prototype of the cubic perovskite.

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Elastic Constants and Thermal Expansion of CsPbCl₃

Cited by 40 publications

References 20 publications

Elastic Anomaly and Phase Transition of BaTiO3

Elastic Anomaly and Phase Transition of BaTiO3

Raman scattering study of the high-temperature vibrational properties and stability of CaGeO3 perovskite

Thermal expansion of SrZrO3 and BaZrO3 perovskites

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Elastic Constants and Thermal Expansion of CsPbCl3

Cited by 40 publications

References 20 publications

Elastic Anomaly and Phase Transition of BaTiO3

Elastic Anomaly and Phase Transition of BaTiO3

Raman scattering study of the high-temperature vibrational properties and stability of CaGeO3 perovskite

Thermal expansion of SrZrO3 and BaZrO3 perovskites

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Elastic Constants and Thermal Expansion of CsPbCl₃