Lattice Instabilities, Anharmonicity and Phase Transitions in PbTiO3 and PbZrO3

1995 ◽  
Vol 408 ◽  
Author(s):  
K. M. Rabe ◽  
U. V. Waghmare
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Cubic Phase ◽  
Temperature Phase ◽  
Structural Phase Transitions ◽  
Phonon Modes ◽  
First Order ◽  
Low Temperature Phase

AbstractMost perovskite structure oxides exhibit structural phase transitions from a hightemperature cubic phase to a distorted low-temperature phase which can be described by the freezing-in of one or more phonon modes of the cubic structure [1]. The first-order cubic-tetragonal ferroelectric transition in PbTiO3 at Tc = 763 K involves the freezing-in of a single F15 polar mode. In PbZrO3 , the structure of the antiferroelectric low-temperature orthorhombic phase is far more complicated, with forty atoms per unit cell and the freezing-in of R25 and Σ3 modes, perhaps accompanied by other modes as well [2][3].

scholarly journals Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
P. S. Whitfield ◽  
N. Herron ◽  
W. E. Guise ◽  
K. Page ◽  
Y. Q. Cheng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Photovoltaic Performance ◽  
Orthorhombic Phase ◽  
Structural Phase Transitions ◽  
Lead Iodide ◽  
First Order ◽  
Hybrid Perovskite ◽  
The Impact

Abstract We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI3) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330 K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ∼ (Tc−T)β, where Tc is the critical temperature and the exponent β was close to ¼, as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160 K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI3 based solar cells.

Structural phase transitions of HfV2 at low temperatures

2000 ◽  
Vol 56 (4) ◽  
pp. 601-606 ◽  
Author(s):  
Yusheng Zhao ◽  
Fuming Chu ◽  
Robert B. Von Dreele ◽  
Qing Zhu
Keyword(s):  
Phase Transitions ◽  
Low Temperatures ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Unit Cell ◽  
The Body ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Structural Phase Transitions ◽  
Low Symmetry

We report a high-resolution synchrotron X-ray powder diffraction study on HfV2, hafnium divanadium, at low temperatures. In this work we show, for the first time, a complete sequence of structural phase transitions of HfV2 from cubic (Fd3m) to tetragonal (I41/amd) to orthorhombic (Imma) in succession as temperature decreases. Peak splitting and extra diffraction peaks owing to lattice distortion can be clearly distinguished for the low-symmetry phases. The atomic positions and lattice parameters were obtained by Rietveld refinement. The bond lengths and angles of the HfV2 crystal structure at the low-symmetry phases were correctly determined from the structure refinement. The face-centered cubic (Fd3m) unit cell (Z = 24) transforms to a body-centered tetragonal (I41/amd) phase with a 45° rotation relative to the cubic cell and with a reduced number of atoms (Z = 12) in the unit cell at a temperature of T = 112 K. The orthorhombic phase occurs at T = 102 K and it keeps the body-centered symmetry (Imma) and Z = 12 in the unit cell. The refinement results indicate that there may be a small amount of untransformed cubic phase left over in the lower symmetry phases. The abnormal thermal contraction of both tetragonal phase and orthorhombic phase marks the significance of structural change in HfV2.

X-ray study of the low-temperature phase transitions in LiKSO4

1983 ◽  
Vol 4 (1) ◽  
pp. 37-45 ◽  
Author(s):  
P. E. Tomaszewski ◽  
K. Łukaszewicz
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
X Ray ◽  
Low Temperature Phase

SHG Microscopic Studies on Low Temperature Phase Transitions of SrTi 16 O 3 and SrTi 18 O 3

2003 ◽  
Vol 285 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Yoshiaki Uesu ◽  
Ryuhei Nakai ◽  
Noritaka Kato ◽  
Carole Menoret ◽  
Jean-Michel Kiat ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
Microscopic Studies ◽  
Low Temperature Phase

Low-temperature phase transitions and dynamics of ammonium in (NH4)3H(SO4)2 and [(NH4)1−x Rbx]3H(SO4)2 crystals

2001 ◽  
Vol 43 (1) ◽  
pp. 117-126 ◽  
Author(s):  
L. S. Smirnov ◽  
A. I. Baranov ◽  
L. A. Shuvalov ◽  
L. Bobrowicz-Sarga ◽  
I. Natkaniec ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
Low Temperature Phase

scholarly journals Macroscopic degeneracy and order in the 3D plaquette Ising model

2015 ◽  
Vol 29 (20) ◽  
pp. 1550109 ◽  
Author(s):  
Desmond A. Johnston ◽  
Marco Mueller ◽  
Wolfhard Janke
Keyword(s):  
Low Temperature ◽  
Magnetic Order ◽  
Finite Size ◽  
Temperature Phase ◽  
Finite Size Scaling ◽  
First Order ◽  
Magnetic Order Parameter ◽  
First Order Transition ◽  
Definition Of ◽  
Low Temperature Phase

The purely plaquette 3D Ising Hamiltonian with the spins living at the vertices of a cubic lattice displays several interesting features. The symmetries of the model lead to a macroscopic degeneracy of the low-temperature phase and prevent the definition of a standard magnetic order parameter. Consideration of the strongly anisotropic limit of the model suggests that a layered, “fuki-nuke” order still exists and we confirm this with multi-canonical simulations. The macroscopic degeneracy of the low-temperature phase also changes the finite-size scaling corrections at the first-order transition in the model and we see this must be taken into account when analyzing our measurements.

Raman study of low temperature phase transitions in the cubic perovskite CH3NH3PbCI3

1998 ◽  
Vol 64 (4) ◽  
pp. 179-190 ◽  
Author(s):  
A. Maaej ◽  
M. Bahri ◽  
Y. Abid ◽  
N. Jaidane ◽  
Z. B. Lakhdar ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Low Temperature ◽  
Temperature Phase ◽  
Raman Study ◽  
Low Temperature Phase
Sign in / Sign up

Export Citation Format

Share Document