Nature of the First-Order Phase Transition in Fluid Phosphorus at High Temperature and Pressure

2003 ◽  
Vol 90 (25) ◽  
Author(s):  
G. Monaco ◽  
S. Falconi ◽  
W. A. Crichton ◽  
M. Mezouar
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
First Order ◽  
High Temperature And Pressure ◽  
First Order Phase Transition ◽  
Temperature And Pressure ◽  
First Order Phase

High Temperature Phase Transitions in BiFeO3

2009 ◽  
Vol 1199 ◽  
Author(s):  
Donna Arnold ◽  
Christopher M Kavanagh ◽  
Philip Lightfoot ◽  
Finlay Doogan Morrison
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
Structure Type ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
First Order ◽  
Β Phase ◽  
First Order Phase Transition ◽  
First Order Phase

AbstractThe high temperature phases of BiFeO3 have courted much controversy with many conflicting structural models reported, in particular for the paraelectric β-phase. High temperature powder neutron diffraction (PND) experiments indicate that the ferroelectric (R3c) α-phase transforms to the paraelectric β-phase at approximately 820 °C via a first order phase transition. We demonstrate that this phase is unambiguously orthorhombic, adopting the GdFeO3 structure-type with a space group Pbnm. On further heating BiFeO3 undergoes another first order phase transition (β-γ) at approximately 930 °C which is marked by a discontinuous decrease in cell volume consistent with an insulator-metal transition. Close inspection of the PND data show no evidence of any symmetry change, with the postulated γ-phase remaining orthorhombic Pbnm. In addition we present PND and impedance spectroscopy data for BiFeO3 which suggest that the so-called ‘Połomska’ transition observed by some authors at approximately 185 °C is not intrinsic.

Synthesis and Lattice Distortion of Ferroelectric/Antiferroelectric Bi(III)-containing Perovskites

2002 ◽  
Vol 755 ◽  
Author(s):  
Yoshiyuki Inaguma ◽  
Atsushi Miyaguchi ◽  
Tetsuhiro Katsumata
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
Lattice Distortion ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
Lattice Distortions ◽  
First Order Phase

ABSTRACTBi(III)-containing perovskites Bi1/2Ag1/2TiO3 and Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni) were synthesized under oxygen pressure as high as approximately 1 MPa and under a pressure as high as 6 GPa, and the lattice distortions were investigated. It was found that ferroelectric Bi1/2Ag1/2TiO3 may be rhombohedrally distorted. In constrast, Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), the structure of which is different from GdFeO3-type compound, is monoclinically distorted. The ratio of lattice parameters of the monoclinic perovskite-subcell for Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), am/bm is larger than that of GdFeO3-type perovskites, though the tolerance factor is close. In addition, it was found that Bi(Ni1/2Ti1/2)O3 undergoes a first-order phase transition from a GdFeO3-type phase(high-temperature phase) at around 490 K. These results indicate that the Bi3+ character in Bi(III)-containing perovskites strongly influences the structure distortion.

scholarly journals First-Order Phase Transformation at Constant Volume: A Continuous Transition?

Entropy ◽  
2021 ◽  
Vol 24 (1) ◽  
pp. 31
Author(s):  
Víctor F. Correa ◽  
Facundo J. Castro
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Order Phase Transition ◽  
Pressure Range ◽  
Constant Volume ◽  
Continuous Transition ◽  
First Order ◽  
First Order Phase Transition ◽  
Temperature And Pressure ◽  
First Order Phase

We describe a first-order phase transition of a simple system in a process where the volume is kept constant. We show that, unlike what happens when the pressure is constant, (i) the transformation extends over a finite temperature (and pressure) range, (ii) each and every extensive potential (internal energy U, enthalpy H, Helmholtz energy F, and Gibbs energy G), and the entropy S is continuous across the transition, and (iii) the constant-volume heat capacity does not diverge during the transition and only exhibits discrete jumps. These non-intuitive results highlight the importance of controlling the correct variables in order to distinguish between continuous and discontinuous transitions. We apply our results to describe the transition between ice VI and liquid water using thermodynamic information available in the literature and also to show that a first-order phase transition driven in isochoric condition can be used as the operating principle of a mechanical actuator.

In Situ Measurement of Phase Transition of Layered Perovskite BaLn2Mn2O7

2010 ◽  
Vol 67 ◽  
pp. 113-117 ◽  
Author(s):  
Hiromi Nakano ◽  
Nobuo Ishizawa ◽  
Hirohisa Sato ◽  
Naoki Kamegashira
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
High Temperature Phase ◽  
Layered Perovskite ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The BaLn2Mn2O7 (Ln = rare earth) has a Sr3Ti2O7-type structure with double block oxygen octahedra belonging to the Ruddlesden-Popper-Type homologous series AO(ABO3)2. In-situ measurement of the phase transition for BaLn2Mn2O7 was performed using single-crystal X-ray diffraction and a high-temperature transmission electron microscope (TEM). Two types of transitions were observed in BaPr2Mn2O7: the transition from primitive tetragonal (P42/mnm) to body-centered tetragonal (I4/mmm) at around 400 K and the first-order phase transition at around 1040 K. Multiple phase transitions were also observed in BaEu2Mn2O7, with one from P42/mnm to I4/mmm at around 400 K and another, above 550 K, as a first-order phase transition. The high-temperature phase had a 1.5% lattice mismatch along the c-axis compared with the low-temperature phase. We succeeded in recording for the first time in-situ structural change in BaGd2Mn2O7 as a movie by high-temperature TEM. The high-temperature phase nucleated parallel to the (00l) plane as a layer above 550 K and grew until covering the entire inspected region at around 1023 K. The first-order phase transition was caused by the structural and/or electrical distortion of the layered perovskite structure composed of Jahn-Teller ion Mn3+.

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

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