scholarly journals Time-Resolved Picosecond Reflectivity Study of Laser-Excited Layered Compounds

1986 ◽  
Vol 74 ◽  
Author(s):  
C. Y. Huang ◽  
A. M. Malvezzi ◽  
N. Bloembergen ◽  
F.J. Di Salvo
Keyword(s):  
Phase Transformation ◽  
Laser Pulses ◽  
High Temperature Phase ◽  
Layered Compounds ◽  
Temperature Phase ◽  
Threshold Fluence ◽  
Time Resolved ◽  
High Fluences ◽  
A Value ◽  
Pump And Probe

AbstractWe have employed the pump-and-probe technique to perform picosecond time resolved measurements of the reflectivity changes in two archetypal layered compounds, IT-TiS2 and lT-TiSe2 probed at 1.064 μm after pumping by 20 ps, .532 μm laser pulses. At the threshold fluence, ∼ 40 mJ/cm2, the reflectivity drops sharply, marking the occurrence of a phase transformation on the surface of the sample. Above threshold, the reflectivity reaches a value as low as ∼0.1 at high fluences, strongly suggesting that, like in graphite, the high temperature phase is not metallic.

Time-Resolved Picosecond Optical Study of Laser-Excited Graphite

1985 ◽  
Vol 51 ◽  
Author(s):  
C. Y. Huang ◽  
A. M. Malvezzi ◽  
J. N. Liu ◽  
N. Bloembergen
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Temperature Gradient ◽  
Threshold Fluence ◽  
Optical Study ◽  
Time Resolved ◽  
High Temperature Gradient ◽  
Probe Technique ◽  
Pump And Probe ◽  
New Phase

ABSTRACTThe pump-and-probe technique is employed to perform picosecond timeresolved measurements of the reflectivity changes in highly oriented pyrolitic graphite excited by 0.532-μm pump pulses. At low pump fluences, the presence of a short-lived plasma and a high-temperature gradient gives rise to an increase in the reflectivity probed at 1.9 μm but causes a decrease at 1.064 μm. At the threshold fluence, 140 mJ/cm2, the reflectivity drops abruptly, marking a phase transformation. Above the threshold, the reflectivity drops to -0.2 from its original value of 0.42 at 1.064 μm and to -0.4 from its ambient value of 0.50 at 1.9 μm. This new phase persists only for a few nanoseconds.

Parameterization of the coupling between strain and order parameter for LuF[SeO3]

2014 ◽  
Vol 47 (2) ◽  
pp. 701-711 ◽  
Author(s):  
Oxana V. Magdysyuk ◽  
Melanie Müller ◽  
Robert E. Dinnebier ◽  
Christian Lipp ◽  
Thomas Schleid
Keyword(s):  
Phase Transition ◽  
Order Parameter ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Time Resolved ◽  
Synchrotron Powder Diffraction ◽  
First Order Phase Transition ◽  
Temperature Phase Transition ◽  
First Order Phase

The high-temperature phase transition of LuF[SeO3] has been characterized by time-resolved high-resolution synchrotron powder diffraction. On heating, a second-order structural phase transition was found at 393 K, while on cooling the same phase transition occurs at 371 K, showing a large hysteresis typical for a first-order phase transition. Detailed analysis using sequential and parametric whole powder pattern fitting revealed that the coupling between the strain and the displacive order parameter determines the behaviour of the material during the phase transition. Different possible coupling mechanisms have been evaluated and the most probable rationalized.

Humidity sensitive irreversible phase transformation of an open-framework Zinc phosphate and its water-assisted high proton conduction properties

2021 ◽  
Author(s):  
Jing-Wei Yu ◽  
Hai-Jiao Yu ◽  
Qiu Ren ◽  
Jin Zhang ◽  
Yang Zou ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Zinc Phosphate ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Open Framework ◽  
High Proton ◽  
Irreversible Phase Transformation ◽  
Low Temperature Phase ◽  
Conduction Properties

Open-framework zinc phosphate (NMe4)(ZnP2O8H3) undergoes irreversible phase transformation. Structural transformation with α (NMe4.Zn[HPO4][H2PO4] the low-temperature phase) and β (NMe4.ZnH3[PO4]2 the high-temperature phase) (Tc=149 °C) and conduction properties were investigated by...

scholarly journals Kinetics of a Phonon-Mediated Laser-Driven Structural Phase Transition in Sn2P2Se6

2019 ◽  
Vol 9 (3) ◽  
pp. 525
Author(s):  
Martin Kubli ◽  
Matteo Savoini ◽  
Elsa Abreu ◽  
Bulat Burganov ◽  
Gabriel Lantz ◽  
...  
Keyword(s):  
Structural Phase ◽  
Higher Order ◽  
High Temperature Phase ◽  
Incommensurate Phase ◽  
Temperature Phase ◽  
Complete Disappearance ◽  
X Ray Diffraction ◽  
Optical Pump ◽  
Time Resolved ◽  
The Time Domain

We investigate the structural dynamics of the incommensurately modulated phase of Sn 2P 2Se 6 by means of time-resolved X-ray diffraction following excitation by an optical pump. Tracking the incommensurable distortion in the time domain enables us to identify the transport effects leading to a complete disappearance of the incommensurate phase over the course of 100 ns. These observations suggest that a thin surface layer of the high-temperature phase forms quickly after photo-excitation and then propagates into the material with a constant velocity of 3.7 m/s. Complementary static structural measurements reveal previously unreported higher-order satellite reflection in the incommensurate phase. These higher-order reflections are attributed to cubic vibrational terms in the Hamiltonian.

Irreversible single-crystal to polycrystal and reversible single-crystal to single-crystal phase transformations in cyanurates

2001 ◽  
Vol 57 (6) ◽  
pp. 791-799 ◽  
Author(s):  
Menahem Kaftory ◽  
Mark Botoshansky ◽  
Moshe Kapon ◽  
Vitaly Shteiman
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Single Crystal ◽  
High Temperature Phase ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
Space Group ◽  
Reversible Phase ◽  
Low Temperature Phase

4,6-Dimethoxy-3-methyldihydrotriazine-2-one (1) undergoes a single-crystal to single-crystal reversible phase transformation at 319 K. The low-temperature phase crystallizes in monoclinic space group P21/n with two crystallographically independent molecules in the asymmetric unit. The high-temperature phase is obtained by heating a single crystal of the low-temperature phase. This phase is orthorhombic, space group Pnma, with the molecules occupying a crystallographic mirror plane. The enthalpy of the transformation is 1.34 kJ mol−1. The small energy difference between the two phases and the minimal atomic movement facilitate the single-crystal to single-crystal reversible phase transformation with no destruction of the crystal lattice. On further heating, the high-temperature phase undergoes methyl rearrangement in the solid state. 2,4,6-Trimethoxy-1,3,5-triazine (3), on the other hand, undergoes an irreversible phase transformation from single-crystal to polycrystalline material at 340 K with an enthalpy of 3.9 kJ mol−1; upon further heating it melts and methyl rearrangement takes place.

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