Soft Modes Responsible for α-β and β-γ Phase Transitions of KIO<sub>3</sub> Crystals

Ahart, Muhtar; Kojima, Seiji; Takagi, Masayoshi; Maeda, Masaki; Suzuki, Ikuo

doi:10.1143/jjap.37.5687

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…At temperature increase the symmetry changes in the sequence triclinic III 345.6 K monoclinic II 485 K trigonal I. The existence of these three phases is confirmed by studies investigating the temperature evolution of physical properties such as nuclear quadrupole resonance, Raman spectroscopy, pyroelectricity, birefringence, dielectric, elastic and piezoelectric properties [1,[7][8][9][10].…”

Section: Introductionmentioning

confidence: 93%

Phase transitions in KIO₃

Bayarjargal

Wiehl

Friedrich

et al. 2012

J. Phys.: Condens. Matter

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The high-pressure behavior of KIO(3) was studied up to 30 GPa using single crystal and powder x-ray diffraction, Raman spectroscopy, second harmonic generation (SHG) experiments and density functional theory (DFT)-based calculations. Triclinic KIO(3) shows two pressure-induced structural phase transitions at 7 GPa and at 14 GPa. Single crystal x-ray diffraction at 8.7(1) GPa was employed to solve the structure of the first high-pressure phase (space group R3, a = 5.89(1) Å, α = 62.4(1)°). The bulk modulus, B, of this phase was obtained by fitting a second order Birch-Murnaghan equation of state (eos) to synchrotron x-ray powder diffraction data resulting in B(exp,second) = 67(3) GPa. The DFT model gave B(DFT,second) = 70.9 GPa, and, for a third order Birch-Murnaghan eos, B(DFT,third) = 67.9 GPa with a pressure derivative of [Formula: see text]. Both high-pressure transformations were detectable by Raman spectroscopy and the observation of second harmonic signals. The presence of strong SHG signals shows that all high-pressure phases are acentric. By using different pressure media, we showed that the transition pressures are very strongly influenced by shear stresses. Earlier work on low- and high-temperature transitions was complemented by low-temperature heat capacity measurements. We found no evidence for the presence of an orientational glass, in contrast to earlier dielectric studies, but consistent with earlier low-temperature diffraction studies.

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Section: Introductionmentioning

confidence: 93%

Phase transitions in KIO₃

Bayarjargal

Wiehl

Friedrich

et al. 2012

J. Phys.: Condens. Matter

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“…According to the structural investigation of Hamid 3) the number of unit molecules in the unit cell changes at T 1 and T 2 . In the Raman scattering experiment 9) it has been reported that three optical soft modes which are related to the successive phase transitions are found and the softening occurs at the Brillouin zone boundaries at T 1 and T 2 . Though clear soft mode was not observed at T 3 the results are consistent with our elastic measurements.…”

Section: Discussionmentioning

confidence: 99%

“…The phase transition at 130 • C reported by several authors is still questionable. 4) Investigations on the physical properties such as dielectric, 2,5) elelctro-optical, 6,7) piezoelectric properties, 6, 7) NQR 2) and Raman scatterng experiments 8,9) of KIO 3 have been reported. Although much data have been reported especially on the temperature dependences of dielectric constants, still there has been some discrepancies between them.…”

Section: §1 Introductionmentioning

confidence: 99%

Temperature Dependences of Dielectric, Elastic and Piezoelectric Properties of KIO₃Single Crystals Associated with the Successive Phase Transitions

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Pottasium iodate, KIO 3 , belongs to the perovskite structure and undergoes successive phase transitions at T 1 = 212 • C, T 2 = 72.5 • C, T 3 = −15 • C, T 4 = −160 • C and T 5 = −240 • C, respectively. The temperature dependences of the dielectric, elastic and piezoelectic properties have been measured in the temperature range from −263 • C to 330 • C. The superionic conductivity was found in the temperature range above T 2 . Pronounced dielectric dispersions in the frequency range below 10 kHz were observed around −160 • C and −240 • C and the data were analyzed by fitting to the Davidson-Cole and Havriliak-Negami dispersion formulas, respectively. Both dielectric anomalies are ascribed to the taional glass-transitions. The piezoelectric and elastic properties have been investigsated by the resonance-antiresonance method. The piezoelectric and elastic anomalies were observed at T 2 and T 3 .Pottasium iodate, KIO 3 , is one of the most facinating member of the perovskite family owing to its non-linerar optical properites. 1) It undergoes successive phase transitions at T 1 = 212 • C, T 2 = 72.5 • C, T 3 = −15 • C and T 4 = −160 • C and T 5 = −240 • C, respectively, and is ferroelectric in all phases below 212 • C. 2) The phases are denoted here I, II, III, IV, V and VI-phases in decending order of the temperature.It has been reported that the space group in each phase is R3m(C 5 3v ) (T > T 1 ), Cm(Cs 3 ) (T 1 > T > T 2 ), and P1(C 1 1 ) (T 2 > T > T 3 ), respectively.3) The results of structural studies on KIO 3 until 1971 were summarized by Crane. 4) The structural details of the I-, II-and III-phases and their relation to the cubic prototype were discussed by Hamid. 2) The structural changes induced by the transitions at T 3 = −15 • C, T 4 = −160 • C and T 5 = −240 • C are not yet known. The phase transition at T 5 was found in the present investigastion. The phase transition at 130 • C reported by several authors is still questionable. 4)Investigations on the physical properties such as dielectric, 2, 5) elelctro-optical, 6, 7) piezoelectric properties, 6, 7) NQR 2) and Raman scatterng experiments 8, 9) of KIO 3 have been reported. Although much data have been reported especially on the temperature dependences of dielectric constants, still there has been some discrepancies between them. The ferroelectric properties of KIO 3 crystals at the successive phase transitions have been investigated in detail by Herlach 2) and Helg, 5) however, the behavior of KIO 3 has not been fully understood. Systematic measurements on the physical properties of KIO 3 have been required to understand the origin of the as 267 successive phase trnsitions.In this paper, dielectric, elastic and piezoelectric measurements have been performed in the temperature range between −263 • C and 330 • C and the mechanism of the successive phase transition has been investigated. §2. ExperimentalThe KIO 3 single crystals used in our experiment were grown from the aqueous solution containg KIO 3 and HIO 3 by the temperature lowering method. 10, ...

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“…Over the past several years, as well as recently, considerable attention has been given to study iodate compounds owing to their interesting properties such as piezoelectric, pyroelectric, and nonlinear optical effects [1][2][3][4]. Some iodates have potential applications in the field of second harmonic generation [5].…”

Section: Introductionmentioning

confidence: 99%

Dielectric behavior and low temperature phase transition in NH₄IO₃

et al. 2012

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The electrical properties namely ac conductivity (!, T) and the complex dielectric permittivity ("*) are measured at selected frequencies (5-100 kHz) as function of temperature (95 K 5 T 5 280 K) for polycrystalline samples of NH 4 IO 3 . The ferroelectric hysteresis loops and the X-ray diffraction pattern are also measured. The analysis of the data indicates that the compound undergoes a structural phase transition at $103 K and the behavior of (!, T ) obeys the power law. The trend of the temperature dependence of the angular frequency exponent s (0 5 s 5 1) suggests that the quantum mechanical tunneling model is the most likely one that describes the conduction mechanism. The core results of the article are: (1) the low temperature ac electrical parameters are measured for NH 4 IO 3 ; (2) the data indicate that the compound undergoes a structural phase transition at 103 K; (3) the originality of this transition has been confirmed by Xray diffraction; (4) no evidence for the existence of a ferroelectric transition at 103 K as mentioned earlier; and (5) the quantum mechanical tunneling is proposed as the main mechanism of the electric conduction.

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Soft Modes Responsible for α-β and β-γ Phase Transitions of KIO₃ Crystals

Cited by 7 publications

References 17 publications

Phase transitions in KIO₃

Phase transitions in KIO₃

Temperature Dependences of Dielectric, Elastic and Piezoelectric Properties of KIO₃Single Crystals Associated with the Successive Phase Transitions

Dielectric behavior and low temperature phase transition in NH₄IO₃

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Soft Modes Responsible for α-β and β-γ Phase Transitions of KIO3 Crystals

Cited by 7 publications

References 17 publications

Phase transitions in KIO3

Phase transitions in KIO3

Temperature Dependences of Dielectric, Elastic and Piezoelectric Properties of KIO3Single Crystals Associated with the Successive Phase Transitions

Dielectric behavior and low temperature phase transition in NH4IO3

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Soft Modes Responsible for α-β and β-γ Phase Transitions of KIO₃ Crystals

Phase transitions in KIO₃

Phase transitions in KIO₃

Temperature Dependences of Dielectric, Elastic and Piezoelectric Properties of KIO₃Single Crystals Associated with the Successive Phase Transitions

Dielectric behavior and low temperature phase transition in NH₄IO₃