scholarly journals Pressure Effects on the Optical Properties of NdVO4

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 237 ◽  
Author(s):  
Enrico Bandiello ◽  
Josu Sánchez-Martín ◽  
Daniel Errandonea ◽  
Marco Bettinelli
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Absorption Band ◽  
Phase Change ◽  
Band Gap ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Pressure Effects ◽  
Absorption Bands ◽  
Fundamental Absorption Band

We report on optical spectroscopic measurements in pure NdVO4 crystals at pressures up to 12 GPa. The influence of pressure on the fundamental absorption band gap and Nd3+ absorption bands has been correlated with structural changes in the crystal. The experiments indicate that a phase transition takes place between 4.7 and 5.4 GPa. We have also determined the pressure dependence of the band-gap and discussed the behavior of the Nd3+ absorption lines under compression. Important changes in the optical properties of NdVO4 occur at the phase transition, which, according to Raman measurements, corresponds to a zircon to monazite phase change. In particular, in these conditions a collapse of the band gap occurs, changing the color of the crystal. The changes are not reversible. The results are analyzed in comparison with those deriving from previous studies on NdVO4 and related vanadates.

scholarly journals Thermo-optical reaction changes of a PCM filled glass system

2021 ◽  
Vol 2069 (1) ◽  
pp. 012195
Author(s):  
T Cabanová ◽  
M Kuruc ◽  
J Čurpek ◽  
D Urbán ◽  
M Čekon
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Phase Change ◽  
Solid Phase ◽  
Spectral Feature ◽  
Heat Of Fusion ◽  
Base Line ◽  
Test Procedures ◽  
Rapid Phase ◽  
Physical Changes

Abstract This paper analyzes thermo-optical reactions of the PCM-based glass element which has the capability to store thermal energy together with a variable transparency level through the energy storage process corresponding to phase change. Optical properties are determined by the level of phase transition at given boundary conditions over time. Special uncommon thermo-optical changes occur during its internal phase transition processes, from liquid to solid phase and vice versa (latent heat of fusion) within a given narrow range of temperature interval. PCM acts as random and diffusive media with relevant scattering effects in solid phase, however in liquid state are highly transparent with direct transmission and no relevant scattering effect. These internal physical changes were detailly identified by experimental test procedures based on optical properties measurements performed using a spectrophotometry, and parallelly with the stabilization of each temperature set provided by environmental chamber. As result of that, relevant differences in the PCM spectral feature can be identified for its different states (solid/liquid) in which transmittance spectra are unstable during rapid phase change process. This provides a substantial base line for the optimization of a PCM glazing system in terms of various degree of freedom for different building types and climate zones.

scholarly journals Optical Properties and Band Gap of Ternary PSN-PMN-PT Single Crystals

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 955
Author(s):  
Wei Long ◽  
Xing Fan ◽  
Pinyang Fang ◽  
Xiaojuan Li ◽  
Zengzhe Xi
Keyword(s):  
Optical Properties ◽  
Single Crystal ◽  
Band Gap ◽  
Structural Changes ◽  
Interband Transition ◽  
Frequency Dispersion ◽  
Domain Size ◽  
Large Lattice ◽  
Application Potential ◽  
Ferroelectric Single Crystal

This study investigated the optical properties and the interband transition of a ternary [100]-oriented 6PSN-61PMN-33PT relaxor ferroelectric single crystal. Compared with the binary [100]-oriented PMN-32PT crystal, the [100]-oriented 6PSN-61PMN-33PT crystal exhibited excellent optical properties, including high transmittance, low refractive index, weak frequency dispersion, and low reflection and absorption coefficients. All these differences can be attributed to the structural changes of the 6PSN-61PMN-33PT crystal, such as its large lattice size and increased band gap. The crystal’s transmittance was significantly improved after alternating current electric field poling due to the increased domain size and the order domain structure. The largest transmittance for the 6PSN-61PMN-33PT crystal was up to 66%. Our experimental results indicate that the ternary 6PSN-61PMN-33PT ferroelectric single crystal has great application potential in the optical field.

Optical Properties of Undoped and Dy3+-Doped Boro-Tellurite Glass

2014 ◽  
Vol 895 ◽  
pp. 194-199 ◽  
Author(s):  
Atiqah Ab Rasid ◽  
Husin Wagiran ◽  
Suhairul Hashim ◽  
Rosli Hussin ◽  
Zuhairi Ibrahim
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Tellurite Glass ◽  
Optical Band Gap ◽  
Band Gap Energy ◽  
Excitation Wavelength ◽  
Absorption Bands ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Doped Glasses

A series of undoped and Dy3+-doped boro-tellurite glasses were prepared, and their optical properties have been studied through XRD, absorption, optical band gap energy and photoluminescence. The XRD pattern has been used to confirm the amorphous nature of the prepared glass. The optical absorption spectra showed eight absorption bands which corresponded to 4I15/2, 4F9/2, 6F3/2, 6F5/2, 6F7/2, 6F9/2, 6F11/2 and 6H11/2 transitions from the ground state, 6H15/2. The optical band gap energy, Eopt for undoped glass was 3.08 eV and the Dy3+-doped glasses Eopt values varied from 3.16 3.24 eV. The emission spectra from photoluminescence spectroscopy showed two dominant emission peaks at 483 nm and 574 nm with an excitation wavelength of 325 nm (3.82 eV). Keywords: X-ray diffraction, boro-tellurite glass, photoluminescence, absorption spectrum, UV-Vis spectroscopy, energy band gap.

Structural Stability and Optical Properties of hexagonal and cubic CdSe Nanocrystals synthesized in MgO

2004 ◽  
Vol 848 ◽  
Author(s):  
S.W.H. Eijt ◽  
van Huis ◽  
P.E. Mijnarends ◽  
B.J. Kooi ◽  
M. Nanu
Keyword(s):  
Optical Properties ◽  
Ion Implantation ◽  
Band Gap ◽  
Structural Changes ◽  
Optical Absorption Spectroscopy ◽  
Cdse Nanocrystals ◽  
High Dose ◽  
Electronic Band ◽  
Supersaturated Solid Solutions ◽  
Direct Band

ABSTRACTWe present a study of CdSe nanocrystals synthesized in MgO by precipitation of Cd and Se supersaturated solid solutions, created in MgO single crystals by ion implantation, in the temperature range between 300 °C and 1100 °C. For high-dose ion implantation, optical absorption spectroscopy revealed the presence of the ∼1.8 eV CdSe semiconductor band-edge. Small sized nanocrystals adopt the rocksalt instead of the wurtzite structure because the former fits better in the MgO matrix and results in lower interface energies. A better understanding of these structural changes and optical properties is obtained from ab-initio total energy calculations on wurtzite, zincblende and rocksalt CdSe using the VASP pseudopotential code. The calculated electronic band structures are compared of zincblende CdSe, a direct band-gap semiconductor, and rocksalt CdSe, which has an indirect optical band-gap.

Pressure Dependence of Photoluminescence of Oligothiophenes

1997 ◽  
Vol 488 ◽  
Author(s):  
L. Rossi ◽  
W. Graupner ◽  
R. Resel ◽  
F. Meghdadi ◽  
G. Leising ◽  
...  
Keyword(s):  
Optical Properties ◽  
Hydrostatic Pressure ◽  
Pressure Dependence ◽  
Structural Changes ◽  
Interchain Coupling ◽  
Conformational Effects

AbstractWe report on the nature of emitting states in two different quaterthiophenes: the unsubstituted quaterthiophenes (T4) and a bridged T4 (T4B), where the bridging have been realized by introducing a second bond between the two central thiophene rings. The effect of the chemical bridging on the photophysics of these compounds have been studied via photoluminescence measurements under hydrostatic pressure, which permit to clarify the influence of interchain coupling, conformational effects and intrachain structural changes on the optical properties.

scholarly journals Enhancing the Optical Properties of Chitosan, Carboxymethyl Cellulose, Sodium Alginate Modified with Nano Metal Oxide and Graphene Oxide

2022 ◽  
Author(s):  
Amina Omar ◽  
Rania Badry ◽  
Maroof A. Hegazy ◽  
Ibrahim S. Yahia ◽  
Hanan Elhaes ◽  
...  
Keyword(s):  
Optical Properties ◽  
Graphene Oxide ◽  
Band Gap ◽  
Sodium Alginate ◽  
Carboxymethyl Cellulose ◽  
Optical Band Gap ◽  
Filler Content ◽  
Nanocomposite Films ◽  
Absorption Bands ◽  
Vis Spectroscopy

Abstract The solution casting method was utilized to synthesize nanocomposite films of chitosan (Cs)/CuO, Cs/graphene oxide (GO), carboxymethyl cellulose (CMC)/TiO2, CMC/GO, sodium alginate (Na Alg)/TiO2, and Na-Alg/GO owing to their various applications. The influence of CuO, TiO2 and GO concentration on the optical properties of Cs, CMC and Na-Alg films was studied by UV-Vis Spectroscopy. The absorbance of Cs, CMC and Na-Alg increased with increasing the filler content, thus reflecting the dependence of Cs, CMC, and Na-Alg properties on the nanofiller content, and confirming the interactions between individual polymers and CuO, TiO2 and GO nanoparticles. The obtained absorbance values were then used to calculate the absorption coefficient and, hence, the optical band gap values. The characteristic absorption bands of CuO and TiO2 underwent a redshift by increasing the filler content. The results showed that the optical band gap of Cs, CMC, and Na-Alg decreased with filler content, and they possessed 1, 2 and 2 band gaps respectively. The obtained results recommended that Cs, CMC, and Na-Alg nanocomposites can be used in optoelectronic devices.

scholarly journals Оптическая спектроскопия и сверхпроводимость купратов (О б з о р)

2019 ◽  
Vol 61 (5) ◽  
pp. 809
Author(s):  
А.С. Москвин
Keyword(s):  
Optical Properties ◽  
Charge Transfer ◽  
High Temperature ◽  
Absorption Band ◽  
High Temperature Superconductors ◽  
Electron Hole ◽  
Electric Polarizability ◽  
Fundamental Absorption Band ◽  
Charge Transfer Transitions ◽  
Low Dimensional

AbstractThe optical properties of low-dimensional dielectric cuprates, including parent systems for high-temperature superconductors, such as La_2CuO_4, Sr_2CuO_2Cl_2, and YBa_2Cu_3O_6 are briefly reviewed. The main focus is on the d – d and p – d charge transfer transitions, which determine the fundamental absorption band. The analysis of optical properties shows the instability of parent cuprates against the d – d charge transfer with the formation of metastable electron–hole (EH) dimers of the Cu^1+–Cu^3+-type pairs coupled by the two-particle transfer and characterized by the giant electric polarizability. The formation of a system of stable EH dimers upon nonisovalent substitution determines the unconventional properties of the pseudogap and superconducting phases of doped cuprates.

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