Infrared reflectance spectroscopy of MgAl2O4 nanoparticles substituted by K+ ions

2018 ◽  
Vol 32 (06) ◽  
pp. 1850067 ◽  
Author(s):  
Javed Ahmad ◽  
M. Qadeer Awan ◽  
Roomana Yasmin ◽  
Maria Sabir ◽  
Shafiq Anwar ◽  
...  
Keyword(s):  
Room Temperature ◽  
Longitudinal Optical ◽  
Reflectance Spectroscopy ◽  
Optical Parameters ◽  
Frequency Range ◽  
Phonon Modes ◽  
Metallic Behavior ◽  
Lorentz Oscillator ◽  
Reflectivity Spectra ◽  
Ftir Spectrometer

The infrared reflectivity spectra for potassium-doped polycrystalline magnesium aluminates Mg[Formula: see text]K[Formula: see text]Al2O4 (x=0, 0.25, 0.50, 0.75, 1) are measured in the frequency range between 10–15, 500 cm[Formula: see text] using FTIR spectrometer at room-temperature. Four optical phonon modes are observed in measured spectra, which are fitted by Lorentz oscillator model for semiconducting behavior and Lorentz–Drude model for metallic behavior. Moreover, optical parameters are also determined for these modes which may attribute to spinel structure for samples Mg[Formula: see text]K[Formula: see text]Al2O4, their reflectivity spectra shows a typical semiconducting nature. To study ionicity and effect of polarization, Born and Szigeti effective charges are calculated from longitudinal optical and transverse optical (LO–TO) splitting of modes for all samples. Optical bandgap has been estimated through optical conductivity ([Formula: see text]([Formula: see text])) and found to be x dependent.

Long-wavelength lattice vibrations of Ag3In5Se9 and Ag3In5Te9 single crystals — An inversion of LO- and TO-mode frequencies

2016 ◽  
Vol 30 (18) ◽  
pp. 1650229 ◽  
Author(s):  
Nizami Mamed Gasanly
Keyword(s):  
Refractive Index ◽  
Single Crystals ◽  
Longitudinal Optical ◽  
Absorption Index ◽  
Energy Losses ◽  
Optical Parameters ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Long Wavelength ◽  
Optical Modes

Infrared (IR) reflectivities are registered in the frequency range of 50–2000 cm[Formula: see text] for Ag3In5Se9 and Ag3In5Te9 single crystals grown by Bridgman method. Three infrared-active modes are detected in spectra. The optical parameters, real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes (TO and LO modes) and oscillator strength were also determined. The bands detected in infrared spectra were tentatively attributed to various vibration types (valence and valence-deformation). The inversion of LO- and TO-mode frequencies of the sandwiched pair was observed for studied crystals.

EFFECT OF SILVER DOPING ON INFRARED REFLECTANCE AND Tc OF SUPERCONDUCTING GdBa2Cu(1−x)3Ag3xO7

1990 ◽  
Vol 04 (11n12) ◽  
pp. 1889-1894
Author(s):  
A. MEMON ◽  
M.N. KHAN ◽  
S. AL-DALLAL ◽  
D.B. TANNER ◽  
C.D. PORTER
Keyword(s):  
Room Temperature ◽  
Phonon Mode ◽  
Resistivity Measurement ◽  
Infrared Reflectance ◽  
Optical Phonons ◽  
Ceramic Superconductor ◽  
Frequency Range ◽  
Phonon Modes ◽  
Silver Doping ◽  
Zero Resistance

Infrared reflectance of GdBa 2 Cu (1−x)3 Ag 3xO7 ceramic superconductor with the composition of x=0.025 and 0.05 have been performed in the frequency range of 100–5000 cm−1. All the infrared active phonon modes allowed by the selection rules were observed in the reflection spectra of these compounds. The optical conductivity as calculated from K-K analysis further confirms the existence of these optical phonons. Besides the increase of the reflectivity in the silver doped samples, an extra phonon mode is observed, which is normally not seen at room temperature reflectance of GdBa 2 Cu 3 O 7 compounds. The four probe resistivity measurement show zero resistance at 88 K for x=0, and 78 K for x=0.025 in GdBa 2 Cu (1−x)3 Ag 3x O 7 compound.

Optical phonons and its effect on physical properties of rare-earth orthoferrites RFeO3 (R = La, Nd, Gd, Dy, Er): IR reflectivity measurements

2018 ◽  
Vol 32 (21) ◽  
pp. 1850229
Author(s):  
Muhammad Tufiq Jamil ◽  
Javed Ahmad ◽  
Syed Hamad Bukhari ◽  
Hammad Ahmad
Keyword(s):  
Sol Gel ◽  
Structural Evolution ◽  
Electrical Measurements ◽  
Phonon Modes ◽  
Lorentz Oscillator ◽  
Reflectivity Spectra ◽  
Visible Spectra ◽  
Atomic Vibrations ◽  
Uv Visible ◽  
Method Analysis

We have investigated the infrared reflectivity, UV-visible spectra and electrical property of polycrystalline RFeO3 (R = La, Nd, Gd, Dy, Er) synthesized by sol–gel method. Analysis of IR reflectivity spectra through Lorentz oscillator model has led to the observation of 14 IR active phonon modes out of 25 predicted modes. The results have been discussed in terms of different phonon bands related to the origin of atomic vibrations, which provides information about the structural evolution. The energy bandgap [Formula: see text]1.67–1.90 eV estimated from optical conductivity ([Formula: see text]([Formula: see text])) spectrum is found consistent both with that calculated from UV-visible spectra and estimated from electrical measurements.

scholarly journals Insight into Structural and Optical Properties of Pristine and Sr2+ Doped La2NiMnO6

2021 ◽  
Vol 58 (2) ◽  
pp. 59-71
Author(s):  
Javed Ahmad ◽  
Shoaib Hassan ◽  
Jamshaid Alam Khan ◽  
Umair Nissar ◽  
Hammad Abbas
Keyword(s):  
Sol Gel ◽  
Average Crystallite Size ◽  
Tangent Loss ◽  
Double Perovskites ◽  
Phonon Modes ◽  
Lorentz Oscillator ◽  
Reflectivity Spectra ◽  
Gel Technique ◽  
A Site ◽  
Insight Into

Double perovskites oxide (DPO) multiferroics La2-xSrxNiMnO6(x=0.0, 0.1, 0.2, 0.4, 0.6) are synthesized by sol-gel technique. The structural, optical and electrical (both DC and AC) properties of La2-xSrxNiMnO6 have been investigated by XRD and FTIR spectroscopy and two-probe resistivity and dielectric measurements as a function of temperature, respectively. The effect of doping of Strontium at A-site in double perovskites is discussed. XRD has revealed the formation of monoclinic structure of La2-xSrxNiMnO6 with space group P21 / n for x=0.0 and P21 for x=0.1, 0.2, 0.4, 0.6. The average crystallite size has been calculated to be in the range 31 to 46 nm as determined by Debye Scherrer equation. Infrared active optical phonons observed from reflectivity spectra have been analysed fitting the theoretical oscillators using Lorentz oscillator model. We have observed several well-resolved phonon modes in La2-xSrxNiMnO6 with increasing dopant concentration. Activation energy calculated using Arrhenius Plot is in the range of 0.31 to 0.18 eV, confirming the semiconducting nature of all samples. The dielectric constant and tangent loss as a function of temperature and frequency are also discussed for these multiferroics.

scholarly journals Lead Telluride Doped with Au as a Very Promising Material for Thermoelectric Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Pantelija M. Nikolic ◽  
Konstantinos M. Paraskevopoulos ◽  
Triantafyllia T. Zorba ◽  
Zorka Z. Vasiljevic ◽  
Eleni Pavlidou ◽  
...  
Keyword(s):  
Electronic Transport ◽  
Room Temperature ◽  
Plasma Frequency ◽  
Lead Telluride ◽  
Far Infrared ◽  
Optical Parameters ◽  
High Quality ◽  
Free Carriers ◽  
Reflectivity Spectra

PbTe single crystals doped with monovalent Au or Cu were grown using the Bridgman method. Far infrared reflectivity spectra were measured at room temperature for all samples and plasma minima were registered. These experimental spectra were numerically analyzed and optical parameters were calculated. All the samples of PbTe doped with Au or Cu were of the “n” type. The properties of these compositions were analyzed and compared with PbTe containing other dopants. The samples of PbTe doped with only 3.3 at% Au were the best among the PbTe + Au samples having the lowest plasma frequency and the highest mobility of free carriers-electrons, while PbTe doped with Cu was the opposite. Samples with the lowest Cu concentration of 0.23 at% Cu had the best properties. Thermal diffusivity and electronic transport properties of the same PbTe doped samples were also investigated using a photoacoustic (PA) method with the transmission detection configuration. The results obtained with the far infrared and photoacoustic characterization of PbTe doped samples were compared and discussed. Both methods confirmed that when PbTe was doped with 3.3 at% Au, thermoelectric and electrical properties of this doped semiconductor were both significantly improved, so Au as a dopant in PbTe could be used as a new high quality thermoelectric material.

scholarly journals Photothermal, Photoelectric, and Photothermoelectric Effects in Bi-Sb Thin Films in the Terahertz Frequency Range at Room Temperature

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 76
Author(s):  
Mikhail K. Khodzitsky ◽  
Petr S. Demchenko ◽  
Dmitry V. Zykov ◽  
Anton D. Zaitsev ◽  
Elena S. Makarova ◽  
...  
Keyword(s):  
Thin Films ◽  
Terahertz Radiation ◽  
Room Temperature ◽  
Voltage Drop ◽  
Radiation Detection ◽  
Radiation Detectors ◽  
Thz Radiation ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range

The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi1−xSbx thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi1−xSbx 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi1−xSbx thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.

scholarly journals Lateral PbS Photovoltaic Devices for High Performance Infrared and Terahertz Photodetectors

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1692
Author(s):  
Emmanuel K. Ampadu ◽  
Jungdong Kim ◽  
Eunsoon Oh
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Photovoltaic Device ◽  
Photovoltaic Devices ◽  
Temperature Spectrum ◽  
Terahertz Region ◽  
Room Temperature Spectrum ◽  
Ftir Spectrometer ◽  
Titanium Substrates ◽  
Deposition Conditions

We fabricated a lateral photovoltaic device for use as infrared to terahertz (THz) detectors by chemically depositing PbS films on titanium substrates. We discussed the material properties of PbS films grown on glass with varying deposition conditions. PbS was deposited on Ti substrates and by taking advantage of the Ti/PbS Schottky junction, we discussed the photocurrent transients as well as the room temperature spectrum response measured by Fourier transform infrared (FTIR) spectrometer. Our photovoltaic PbS device operates at room temperature for wavelength ranges up to 50 µm, which is in the terahertz region, making the device highly applicable in many fields.

scholarly journals Dielectric Spectroscopy Analysis of Liquid Crystals Recovered from End-of-Life Liquid Crystal Displays

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2873
Author(s):  
Ana Barrera ◽  
Corinne Binet ◽  
Frédéric Dubois ◽  
Pierre-Alexandre Hébert ◽  
Philippe Supiot ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
End Of Life ◽  
Room Temperature ◽  
Liquid Crystal Displays ◽  
Dielectric Anisotropy ◽  
Frequency Range ◽  
Spectroscopy Analysis ◽  
Diamond Nanoparticles ◽  
Nematic Phases ◽  
Universal Law

In the present work, the dielectric properties of recycled liquid crystals (LCs) (non-purified, purified, and doped with diamond nanoparticles at 0.05, 0.1, and 0.2 wt%) were investigated. The studied LC mixtures were obtained from industrial recycling of end-of-life LC displays presenting mainly nematic phases. Dielectric measurements were carried out at room temperature on a frequency range from 0.1 to 106 Hz using an impedance analyzer. The amplitude of the oscillating voltage was fixed at 1 V using cells with homogeneous and homeotropic alignments. Results show that the dielectric anisotropy of all purified samples presents positive values and decreases after the addition of diamond nanoparticles to the LC mixtures. DC conductivity values were obtained by applying the universal law of dielectric response proposed by Jonscher. In addition, conductivity of the doped LC mixtures is lower than that of the undoped and non-purified LC.

High Frequency Dielectric Response of the Ionic Liquid N-Methyl-N-ethylpyrrolidinium Dicyanamide

2007 ◽  
Vol 60 (1) ◽  
pp. 6 ◽  
Author(s):  
Simon Schrödle ◽  
Gary Annat ◽  
Douglas R. MacFarlane ◽  
Maria Forsyth ◽  
Richard Buchner ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Dielectric Loss ◽  
Dielectric Relaxation ◽  
High Frequency ◽  
Dielectric Response ◽  
Room Temperature ◽  
Room Temperature Ionic Liquid ◽  
Dielectric Relaxation Spectroscopy ◽  
Frequency Range ◽  
Fast Rotation

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ≤ ν ≤ 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation.

scholarly journals Оптические свойства фазопеременных материалов системы германий--сурьма-теллур составов Ge-=SUB=-14-=/SUB=-Sb-=SUB=-29-=/SUB=-Te-=SUB=-57-=/SUB=- и Ge-=SUB=-15-=/SUB=-Sb-=SUB=-15-=/SUB=-Te-=SUB=-70-=/SUB=- в дальнем инфракрасном диапазоне

2021 ◽  
Vol 55 (7) ◽  
pp. 542
Author(s):  
В.А. Рыжов ◽  
Б.Т. Мелех ◽  
Л.П. Казакова
Keyword(s):  
Amorphous Alloy ◽  
Infrared Absorption ◽  
Crystalline State ◽  
Room Temperature ◽  
Torsional Vibrations ◽  
Phonon Modes ◽  
Absorption Bands ◽  
Structural Units ◽  
Chalcogenide Alloys ◽  
Infrared Absorption Spectra

Abstract Infrared absorption spectra of chalcogenide alloys of the GST system with the compositions Ge14Sb29Te57 and Ge15Sb15Te70 in the amorphous and crystalline state were measured and analyzed in the range of 20 – 400 cm– 1 (0.6 – 12 THz) at room temperature. Absorption at these frequencies is due to the manifestation of correlated torsional vibrations of structural units of the amorphous alloy and phonon modes of the crystal. The performed assignment of absorption bands and the revealed differences in the IR spectra make it possible to more confidently represent the possible molecular mechanism of reversible amorphous-crystalline transformations in the studied phase-changing materials

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