Exafs Studies of Semiconductors

1986 ◽  
Vol 77 ◽  
Author(s):  
Bruce A. Bunker
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Exafs Spectroscopy ◽  
Nondestructive Measurement ◽  
Bond Lengths ◽  
Fe Impurities

ABSTRACTRecent results from EXAFS spectroscopy are discussed, including (i) the determination of the site and local bond lengths of Fe impurities implanted into Si, (ii) the determination of the ferroelectric phase transition in Pb1−x Gex Te as order-disorder rather than displacive, and (iii) the nondestructive measurement of Aℓ diffusion into GaAs at an Aℓ/GaAs Interface.

Dielectric Study of the Ferroelectric Phase Transition in DMAGaS Crystal

1998 ◽  
Vol 53 (3-4) ◽  
pp. 105-111 ◽  
Author(s):  
R. Tchukvinskyi ◽  
R. Cach ◽  
Z. Czapla
Keyword(s):  
Phase Transition ◽  
Electric Field ◽  
Ferroelectric Phase Transition ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Dielectric Study ◽  
Electric Permittivity ◽  
First Order ◽  
Dc Electric Field

Abstract Electric permittivity measurments as functions of temperature at constant dc electric field and as functions of the dc electric field at constant temperatures in the paraelectric phase have been performed for DMAGaS crystal. The changes of the permittivity maximum with the electric field intensity evidence the first-order character of the ferroelectric phase transition at Tc1. The field dependence of the permittivity ε(E) in the paraelectric phase is discussed, using the classical electric equation of state. A method for the determination of the corresponding coefficients is proposed. The obtained B and C coefficients, together with double hysteresis loop observed above Tc1 prove the first-order character of the ferroelectric phase transition in DMAGaS crystal.

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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