The specific heat of the ferroelectric phase transition in N(CH3)4CdBr3

1994 ◽  
Vol 41 (6) ◽  
pp. 1211-1215 ◽  
Author(s):  
J. M. Igartua ◽  
G. Aguirre-Zamalloa ◽  
I. Ruiz-Larrea ◽  
M. Couzi ◽  
A. López-Echarri ◽  
...  
Keyword(s):  
Phase Transition ◽  
Specific Heat ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase

Calorimetric study of ferroelectric BaTiO3 in cubic phase

2013 ◽  
Vol 03 (04) ◽  
pp. 1350032 ◽  
Author(s):  
S. V. Grabovsky ◽  
I. V. Shnaidshtein ◽  
M. Takesada ◽  
A. Onodera ◽  
B. A. Strukov
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Specific Heat ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Cubic Phase ◽  
Calorimetric Study ◽  
Good Accordance ◽  
Top Seeded Solution Growth

Specific heat of barium titanate single crystals of different quality has been precisely measured with special attention to the temperature region above the ferroelectric phase transition. It was assumed that excess specific heat in the paraelectric phase has a fluctuation nature and the experimental data were analyzed in the framework of Levanyuk's theory for multiaxial ferroelectrics. Within this approach the correlation parameter δ is estimated to be 0.66 × 10-16 cm2 for Remeika-type crystals and 0.45 × 10-16 cm2 for TSSG (top-seeded solution growth) crystals. These values are in good accordance with earlier estimations.

scholarly journals The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Đorđe Dangić ◽  
Olle Hellman ◽  
Stephen Fahy ◽  
Ivana Savić
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transitions ◽  
Thermoelectric Materials ◽  
Ferroelectric Phase Transition ◽  
Lattice Thermal Conductivity ◽  
Ferroelectric Phase ◽  
Structural Phase ◽  
High Symmetry ◽  
Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

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