Theory of order–disorder phase transitions of B-cations in AB′1/2 B′′1/2O3 perovskites

2018 ◽  
Vol 74 (3) ◽  
pp. 264-273 ◽  
Author(s):  
V. P. Sakhnenko ◽  
N. V. Ter-Oganessian
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Sample Treatment ◽  
Double Perovskites ◽  
Synthesis Conditions ◽  
Disorder Phase Transition ◽  
Lattice Constants ◽  
Cation Order ◽  
Phase Transition Temperatures ◽  
Subsequent Sample

Perovskite-like oxides AB′1/2 B′′1/2O3 with two different cations in the B-sublattice may experience cation order–disorder phase transitions. In many cases the degree of cation ordering can be varied by suitable synthesis conditions or subsequent sample treatment, which has a fundamental impact on the physical properties of such compounds. Therefore, understanding the mechanism of cation order–disorder phase transition and estimation of the phase transition temperature is of paramount importance for tuning of properties of such double perovskites. In this work, based on the earlier proposed cation–anion elastic bonds model, a theory of order–disorder phase transitions of B-cations in AB′1/2 B′′1/2O3 perovskites is presented, which allows reliable estimation of the phase transition temperatures and of the reduced lattice constants of such double perovskites.

scholarly journals Effect of pressure on the order–disorder phase transitions of B cations in AB′1/2 B′′1/2O3 perovskites

2019 ◽  
Vol 75 (6) ◽  
pp. 1034-1041
Author(s):  
Nikita V. Ter-Oganessian ◽  
Vladimir P. Sakhnenko
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Statistical Model ◽  
Atomic Order ◽  
Atomic Ordering ◽  
Synthesis Conditions ◽  
Disorder Phase Transition ◽  
Effect Of Pressure ◽  
Post Synthesis

Perovskite-like oxides AB′1/2 B′′1/2O3 may experience different degrees of ordering of the B cations that can be varied by suitable synthesis conditions or post-synthesis treatment. In this work the earlier proposed statistical model of order–disorder phase transitions of B cations is extended to account for the effect of pressure. Depending on the composition, pressure is found to either increase or decrease the order–disorder phase transition temperature. The change in transition temperature due to pressure in many cases reaches several hundred kelvin at pressures accessible in the laboratory, which may significantly change the degree of atomic ordering. The work is intended to help in determining how pressure influences the degree of atomic ordering and to stimulate research into the effect of pressure on atomic order–disorder phase transitions in perovskites.

scholarly journals Thermal, ferroelastic, and structural properties near phase transitions of organic–inorganic perovskite type [NH3(CH2)3NH3]CdBr4 crystals

RSC Advances ◽  
2021 ◽  
Vol 11 (29) ◽  
pp. 17622-17629
Author(s):  
Ae Ran Lim
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Thermal Behavior ◽  
Structural Properties ◽  
Structural Dynamics ◽  
Transition Temperatures ◽  
Inorganic Perovskite ◽  
Phase Transition Temperatures ◽  
Perovskite Type

We studied the thermal behavior and structural dynamics of [NH3(CH2)3NH3]CdBr4 near phase transition temperatures.

INDUCED CHANGES OF THERMOTROPIC PROPERTIES OF PHASE TRANSITIONS BETWEEN SMECTIC A MESOPHASE AND ISOTROPIC LIQUID: EFFECT OF SURFACES

2006 ◽  
Vol 20 (14) ◽  
pp. 821-833 ◽  
Author(s):  
ARIF NESRULLAJEV ◽  
ŞENER OKTIK
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transition ◽  
Phase Transitions ◽  
Isotropic Liquid ◽  
Smectic A ◽  
Phase Transition Temperatures ◽  
Smectic A Phase ◽  
Induced Changes ◽  
Thermotropic Properties

In this work, the effect of thin films on the thermotropic and thermo-optical properties and peculiarities of the phase transitions between the smectic A and isotropic liquid have been investigated. Peculiarities of the heterophase regions of the straight smectic A-isotropic liquid and reverse isotropic liquid-smectic A phase transitions have been studied. Change of morphologic properties of the heterophase regions, shift of the phase transition temperatures and the change of temperature widths of these heterophase regions under thin film influence have been observed.

Mössbauer Studies of Fe2+ in Iron Langbeinites and other Crystals with Langbeinite Structure

1998 ◽  
Vol 53 (1-2) ◽  
pp. 27-37 ◽  
Author(s):  
M. Windhaus ◽  
B. D. Mosel ◽  
W. Müller-Warmuth
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Low Temperature ◽  
High Spin State ◽  
Cubic Phases ◽  
Debye Temperatures ◽  
Phase Transition Temperatures ◽  
Abrupt Changes ◽  
Temperature Dependences

Abstract 57 Fe Mössbauer spectra have been measured at various temperatures between 4.2 K and 300 K for iron langbeinites A 2 Fe 2^04)3 with A = K, NH 4 , Rb, T1 and magnesium, manganese and cadmium lang-beinites doped with Fe" + . The spectra revealed several contributions whose isomer shifts and quadru-pole splittings have been obtained by fitting program routines. For the high-temperature cubic phases two crystallographically non-equivalent iron sites have been identified, characteristic of Fe2+ in the high-spin state. Abrupt changes of the quadrupole couplings indicated phase transitions; in some cases, the spectra have also revealed several sites for Fe2+ in low temperature phases. From the temperature dependences, phase transition temperatures, crystal field splittings and Debye temperatures have been derived.

Liquid Crystalline Norcholesterylesters: Influence of the Axial Methylgroups on the Phase Transitions and the Cholesteric Helix

1989 ◽  
Vol 44 (11) ◽  
pp. 1127-1130 ◽  
Author(s):  
H. Stegemeyer ◽  
K. Siemensmeyer ◽  
W. Sucrow ◽  
L. Appel
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Liquid Crystalline ◽  
Helical Structure ◽  
Transition Temperatures ◽  
Phase Transition Temperatures

Liquid crystalline norcholesteryl anisic esters were prepared in which the methylgroups 19, 21, 27, and 18 are removed successively from the cholestene skeleton. The influence of the axial methylgroups on the phase transition temperatures and the choleric helical structure has been investigated. On heating the 18.19.21.27-tetranorcholesteryl ester, at 155 °C an inversion of the helical screw sense from left to right was observed

Phase transitions of (1−x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions

1999 ◽  
Vol 14 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Jung-Kun Lee ◽  
Hyuk-Joon Youn ◽  
Kug Sun Hong
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Solutions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Phase Transition Temperatures ◽  
Temperature Phase Transition ◽  
Increasing Temperature

Morphotropic phase boundaries and temperature dependent phase transitions of (1 – x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions were investigated by x-ray diffraction, differential scanning calorimetry (DSC), and dielectric property analysis. Two morphotropic phase transitions at room temperature were found at x = 0.1 and 0.13, which were from antiferroelectric orthorhombic (with 4 × 4 × 2 superlattice [orthorhombic (I)]) to antiferroelectric orthorhombic (with 2 × 2 × 2 superlattice [orthorhombic (II)]) and from orthorhombic (II) to ferroelectric rhombohedral, respectively. With increasing temperature, the samples with 0.01 ≤ x < 0.1 showed two phase transitions, i.e., from orthorhombic (I) to orthorhombic (II) and from orthorhombic (II) to cubic. The other samples had only one phase transition with increasing temperature. Phase transition temperatures of all the samples were measured using DSC, and a phase diagram for the solid solutions was constructed. A model illustrating the antiparallel shift of Pb ions in the orthorhombic (II) phase was also proposed.

Ultra-fast Time-Resolved Electron Diffraction of Strongly Driven Phase Transitions on Silicon Surfaces

2009 ◽  
Vol 1230 ◽  
Author(s):  
Simone Möllenbeck ◽  
Anja Hanisch-Blicharski ◽  
Paul Schneider ◽  
Manuel Ligges ◽  
Ping Zhou ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Electron Diffraction ◽  
Structural Phase ◽  
High Energy ◽  
Silicon Surfaces ◽  
Fast Time ◽  
Time Resolved ◽  
Disorder Phase Transition ◽  
Pulse Pump

AbstractThe dynamics of strongly driven phase transitions at surfaces are studied by ultra-fast time-resolved reflection high energy electron diffraction. The surfaces are excited by an intense fs-laser pulse (pump) and probed by an ultra-short electron pulse with variable time delay. The order-disorder phase transition from a c(4×2) to a (2×1) of the bare Si(001) surface shows a transient decrease of the intensity of the c(4×2) spots which recovers on a time scale of a few hundred picoseconds indicating the excitation of the phase transition. On Si(111) a monolayer of Indium induces a (4×1) reconstruction which undergoes a Peierls like phase transition to a (8ד2”) reconstruction below 100 K. Upon laser excitation at a temperature of 40 K the phase transition was strongly driven. The (8ד2”)-diffraction spots instantaneously disappears, while the intensity of the (4×1)-spots increases. This increase of the (4×1) spot intensity excludes an explanation by the Debye-Waller-Effect and is evidence for a true structural phase transition at a surface.

scholarly journals Влияние структурных неоднородностей и газообразующих примесей на функциональные свойства высокочистых редкоземельных металлов

2018 ◽  
Vol 60 (6) ◽  
pp. 1103
Author(s):  
В.Б. Чжан ◽  
И.С. Терёшина
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Magnetocaloric Effect ◽  
Magnetic Phase Transition ◽  
Structural State ◽  
Magnetic Order ◽  
Magnetic Phase ◽  
Grain Sizes ◽  
Phase Transition Temperatures ◽  
Curie Temperatures

AbstractRare-earth metals (REM) gadolinium and dysprosium, and also the Gd–H and Dy–H systems in which magnetic order–order and order–disorder phase transitions are accompanied by significant magnetocaloric effect, have been studied. The materials have been prepared in various structural states. It is stated that there is a substantial difference of their functional properties in the dependence on the features of the structural state and also on the existence of a gas-forming impurity. It has been proved experimentally and theoretically that the Curie temperatures of Gd samples with grain sizes of ~200 nm increases as a result of hydrogenation, while the magnetic phase transition temperatures of Dy are almost unchanged Inhomogeneities.

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