Green’s-function theory of ferroelectric phase transitions in hydrogen-bonded triglycine sulfate with the pseudospin-lattice coupled-mode model: A unified theory of structural phase transitions. II. Nonlinear properties

1988 ◽  
Vol 38 (1) ◽  
pp. 708-714 ◽  
Author(s):  
B. K. Chaudhuri ◽  
K. R. Choudhury ◽  
Suvra Banerjee
Keyword(s):  
Phase Transitions ◽  
Ferroelectric Phase ◽  
Function Theory ◽  
Structural Phase ◽  
Triglycine Sulfate ◽  
Unified Theory ◽  
Structural Phase Transitions ◽  
Nonlinear Properties ◽  
Coupled Mode ◽  
Ferroelectric Phase Transitions

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.

Unified theory of ferroelectric phase transitions: Quantum limit

1977 ◽  
Vol 43 (1) ◽  
pp. 99-103 ◽  
Author(s):  
S. Stamenković ◽  
N. M. Plakida ◽  
V. L. Aksienov ◽  
T. Siklós
Keyword(s):  
Phase Transitions ◽  
Ferroelectric Phase ◽  
Quantum Limit ◽  
Unified Theory ◽  
Ferroelectric Phase Transitions

Unified theory of ferroelectric phase transitions

1976 ◽  
Vol 14 (11) ◽  
pp. 5080-5087 ◽  
Author(s):  
S. Stamenković ◽  
N. M. Plakida ◽  
V. L. Aksienov ◽  
T. Siklós
Keyword(s):  
Phase Transitions ◽  
Ferroelectric Phase ◽  
Unified Theory ◽  
Ferroelectric Phase Transitions

Optical nonlinear properties and structural phase transitions in a new promising ferroelectric family LnBXO 5 (Ln-La, Pr; X-Ge, Si)

1997 ◽  
Author(s):  
B. A. Strukov ◽  
B. V. Mill ◽  
Eleva L. Belokoneva ◽  
S. Y. Stefanovich ◽  
V. N. Sigaev ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Nonlinear Properties

scholarly journals Influence of Relaxing Defects on the Paraelectric-Ferroelectric Phase Transitions of Rochelle Salt

1979 ◽  
Vol 34 (5) ◽  
pp. 538-547 ◽  
Author(s):  
J. Petersson
Keyword(s):  
Phase Transitions ◽  
Ferroelectric Phase ◽  
Cell Model ◽  
Structural Phase ◽  
Crystal Defects ◽  
General Description ◽  
Rochelle Salt ◽  
Dielectric Polarization ◽  
Salt Crystals ◽  
Ferroelectric Phase Transitions

Abstract It is well known that different types of crystal defects influence the static and dynamic behaviour of the dielectric polarization of Rochelle salt crystals. Particularly strong effects appear near the paraelectric-ferroelectric phase transitions. In this paper it is shown that a slightly modified relaxing defect cell model which has been developed [1] in order to explain the narrow central peaks observed near structural phase transitions adequately describes the interaction between the strongly temperature dependent relaxational motion of the order parameter and the relaxational motions of the various defect modes. This theory is shown to be equivalent to a phenomenological Landau Khalatnikov approach, which so far has only been used to characterize the macroscopic dielectric behaviour of Rochelle salt crystals with defects near the phase transitions, and which in a previous work [16], has been developed in order to give a general description of central peak phenomena caused by defects. For instance the so called very fast after effect and its influence on the phase transitions is discussed in more detail.

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