Logarithmic singularity in the specific heat in the vicinity of phase transitions in uniaxial ferroelectrics

Strukov, B. A.; Ragula, E. P.; Arkhangel’skaya, S. V.; Shnaĭdshteĭn, I. V.

doi:10.1134/1.1130241

Cited by 11 publications

(19 citation statements)

References 6 publications

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“…It has been already pointed that in uniaxial ferroelectrics of order-disorder type like TGS or KDP the polarization fluctuation contribution to specific heat is suppressed and quite small [12,13]. In case of the multiaxial barium titanate, which cubic in the paraelectric phase, a situation is quite different.…”

Section: Resultsmentioning

confidence: 99%

Calorimetric study of ferroelectric BaTiO₃ in cubic phase

et al. 2013

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Precise specific heat of barium titanate single crystals of different quality has been measured with special attention to the temperature region above the ferroelectric phase transition. It is shown that excess specific heat of the multiaxial barium titanate in the paraelectric phase has a fluctuation nature and its temperature dependence is in accordance with the theoretical predictions of Levanyuk theory for multiaxial ferroelectrics. In this study the first observation of fluctuation contribution to the specific heat is presented. The correlation parameter δ is estimated to be 0.66×10 −16 cm 2 for Remeika-type crystals and 0.45×10 −16 cm 2 for TSSG (top-seeded solution growth) crystals.

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Section: Resultsmentioning

confidence: 99%

Calorimetric study of ferroelectric BaTiO₃ in cubic phase

et al. 2013

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“…These bonds are responsible for the ferroelectric phase transitions found in ammonium and rubidium hydrogen sulphates [2,3]. From earlier dielectric measurements [2,4], it was inferred that NH 4 HSO 4 (AHS) undergoes two phase transitions at normal pressure, at T 1 = -3 °C (second order) and T 2 = -119 °C (first order), respectively. The phase behaviour of AHS has been studied by thermal and electrical measurements [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…It is relatively common that salts with hydrogen bonds have a high-temperature phase with high proton mobility, while the low temperature phases are ferroelectric (FE) or antiferroelectric (AFE). The family MHSO 4 (M = K, Rb, Cs and NH 4 ) forms an interesting group of materials characterized by the presence of a hydrogen bonding pattern between the 4 HSOtetrahedral ions [1]. These bonds are responsible for the ferroelectric phase transitions found in ammonium and rubidium hydrogen sulphates [2,3].…”

Section: Introductionmentioning

confidence: 99%

On the high‐temperature phase transitions of NH₄HSO₄

Diosa

Fernández

Vargas

et al. 2005

Physica Status Solidi (a)

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64.70.Kb, 81.70.Pg Modulated differential scanning calorimetry (MDSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to study the phase behaviour of NH 4 HSO 4 (AHS) above room temperature. For powder AHS measured during successive thermal cycles, the MDSC curves show an endothermic peak at 147 °C on heating scans and an exothermic peak at about 115 °C on subsequent cooling runs. However, after the second thermal cycle, a second endothermic peak starts to appear at about 135 °C on heating runs whose intensity increases on subsequent cycles. The thermogravimetric measurements on powder AHS show weight loss above 135 °C. X-ray powder diffraction data for AHS heated to 140 °C during 24 hours, show the diffraction pattern for (NH 4 ) 2 S 2 O 7 . We discuss the endothermic effect at 135 °C in terms of a partial dehydration setting in at reaction sites distributed on the surface of the crystals.

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“…7-18 Adiabatic measurements 7 made near T C on powdered TGS samples were puzzling in the sense that for the first time, in the field of ferroelectrics, the specific-heat anomaly for a continuous transition was not of the type. Seeking to clarify the experimental situation, Strukov et al 16 performed high-accuracy adiabatic specific-heat measurements and set limits on the relative measurement accuracy needed for observing critical fluctuations near T C . 19 High-sensitivity ac measurements of the Seidel type 20 made on short-circuited crystals, showed a pronounced anomaly at T C .…”

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“…It was therefore anticipated that because ͑a͒ surface excitations are known to affect the bulk thermodynamic properties at low-temperature giving rise to a T 3/2 term, 22 ͑b͒ nongrounded powders do not give the expected anomaly at T C , 7 ͑c͒ ac measurements show a pronounced anomaly with a logarithmic critical fluctuations, 14,18 and ͑d͒ highprecision adiabatic measurements show a smearing of the transition and do not have a logarithmic singularity, 16 surface excitations generated from the pyroelectric coefficient, dP / dT, were affecting the nature of the specific-heat anomaly near T C .…”

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Heat capacity in magnetic and electric fields near the ferroelectric transition in triglycine sulfate

Lashley

Hundley

Mihaila

et al. 2007

Applied Physics Letters

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Articles you may be interested in[N(CH3)3H]2ZnCl4: Ferroelectric properties and characterization of phase transitions by Raman spectroscopy Large electrocaloric effect induced by the multi-domain to mono-domain transition in ferroelectricsSpecific-heat measurements are reported near the Curie temperature ͑T C = 320 K͒ on triglycine sulfate. Measurements were made on crystals whose surfaces were either nongrounded or short circuited, and were carried out in magnetic fields up to 9 T and electric fields up to 220 V / cm. In nongrounded crystals the authors find that the shape of the specific-heat anomaly near T C is thermally broadened. However, the anomaly changes to the characteristic sharp shape expected for a continuous transition with the application of either a magnetic field or an electric field. In crystals whose surfaces were short circuited with gold, the characteristic shape appeared in the absence of an external field. This effect enabled a determination of the critical exponents above and below T C , and may be understood on the basis that the surface charge originating from the pyroelectric coefficient, dP / dT, behaves as if shorted by external magnetic or electric fields.

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Logarithmic singularity in the specific heat in the vicinity of phase transitions in uniaxial ferroelectrics

Cited by 11 publications

References 6 publications

Calorimetric study of ferroelectric BaTiO₃ in cubic phase

Calorimetric study of ferroelectric BaTiO₃ in cubic phase

On the high‐temperature phase transitions of NH₄HSO₄

Heat capacity in magnetic and electric fields near the ferroelectric transition in triglycine sulfate

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Logarithmic singularity in the specific heat in the vicinity of phase transitions in uniaxial ferroelectrics

Cited by 11 publications

References 6 publications

Calorimetric study of ferroelectric BaTiO3 in cubic phase

Calorimetric study of ferroelectric BaTiO3 in cubic phase

On the high‐temperature phase transitions of NH4HSO4

Heat capacity in magnetic and electric fields near the ferroelectric transition in triglycine sulfate

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Product

Resources

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Calorimetric study of ferroelectric BaTiO₃ in cubic phase

Calorimetric study of ferroelectric BaTiO₃ in cubic phase

On the high‐temperature phase transitions of NH₄HSO₄