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Rare earth zirconate ceramic has been considered as one of the potential thermal barrier coating materials to replace 6–8% YSZ material (6–8% yttrium oxide stabilized zirconia), because of its low thermal conductivity and good high temperature phase stability. However, there is a problem that the coefficient of thermal expansion does not match the matrix. In this paper, rare earth high entropy zirconate ceramic powder with defective fluorite structure was prepared by molten salt synthesis(MSS). The results show that the reaction temperature and the ratio of reactants to molten salt will affect the synthesis effects. With the action of the high entropy effect, the synthesized ceramic powder has low thermal conductivity, improved thermal expansion coefficient and high infrared reflectivity. [ABSTRACT FROM AUTHOR]

Functional energy-saving materials with coupled cooling effect have become particularly urgent because traditional cooling systems require high industrial energy inputs and high labor costs. Biomass-derived materials are highly desirable for the environment and energy-related applications, but raw biomass materials cannot satisfy cooling demands for more environment and energy-efficient processes. Herein, inspired by the transpiration of natural plants and radiation cooling of metal materials, this study presents the silver nanoparticles–coated wood with a coupled cooling effect for dual-mode cooling. The silver nanoparticles–coated wood with a natural hollow ordered pore structure can achieve the cooling effect by the capillary phenomenon where water absorption and evaporation. The results revealed that silver nanoparticles with high infrared reflectivity were firmly embedded in the surface of the wood by magnetron sputtering, which empowers the wood with high infrared heat dissipation properties. Compared to the bare porous wood, the surface temperatures of silver nanoparticles coated wood were decreased from 34.6–35.8 to 30.3–31.2 °C. In addition, by combining with the evaporative and radiative heat dissipation, the silver-coated wood obtained the coupled cooling effect under simulated solar radiation, which further improves the cooling effect. Owing to the silver coating, the material possesses an excellent antibacterial property which extends durability. Therefore, the tree-inspired water vapor evaporation and radiation cooling show good harmony and can be well combined by the directional structure design of the material. This dual-mode cooling mechanism provides a novel design concept of cooling materials and further promises to benefit the sustainability of society in many aspects, from health to economy. [ABSTRACT FROM AUTHOR]

The halide perovskite TiF3, renowned for its intricate interplay between structure, electronic correlations, magnetism, and thermal expansion, is investigated. Despite its simple structure, understanding its low‐temperature magnetic behavior has been a challenge. Previous theories propose antiferromagnetic ordering. In contrast, experimental signatures for an ordered magnetic state are absent down to 10 K. The current study has successfully reevaluated the theoretical modeling of TiF3, unveiling the significance of strong electronic correlations as the key driver for its insulating behavior and magnetic frustration. In addition, frequency‐dependent optical reflectivity measurements exhibit clear signs of an insulating state. The analysis of the calculated magnetic data gives an antiferromagnetic exchange coupling with a net Weiss temperature of order 25 K as well as a magnetic response consistent with a S = 1/2 local moment per Ti3+. Yet, the system shows no susceptibility peak at this temperature scale and appears free of long‐range antiferromagnetic order down to 1 K. Extending ab initio modeling of the material to larger unit cells shows a tendency for relaxing into a noncollinear magnetic ordering, with a shallow energy landscape between several magnetic ground states, promoting the status of this simple, nearly cubic perovskite structured material as a candidate spin liquid. [ABSTRACT FROM AUTHOR]

The halide perovskite TiF3, renowned for its intricate interplay between structure, electronic correlations, magnetism, and thermal expansion, is investigated. Despite its simple structure, understanding its low‐temperature magnetic behavior has been a challenge. Previous theories propose antiferromagnetic ordering. In contrast, experimental signatures for an ordered magnetic state are absent down to 10 K. The current study has successfully reevaluated the theoretical modeling of TiF3, unveiling the significance of strong electronic correlations as the key driver for its insulating behavior and magnetic frustration. In addition, frequency‐dependent optical reflectivity measurements exhibit clear signs of an insulating state. The analysis of the calculated magnetic data gives an antiferromagnetic exchange coupling with a net Weiss temperature of order 25 K as well as a magnetic response consistent with a S = 1/2 local moment per Ti3+. Yet, the system shows no susceptibility peak at this temperature scale and appears free of long‐range antiferromagnetic order down to 1 K. Extending ab initio modeling of the material to larger unit cells shows a tendency for relaxing into a noncollinear magnetic ordering, with a shallow energy landscape between several magnetic ground states, promoting the status of this simple, nearly cubic perovskite structured material as a candidate spin liquid. [ABSTRACT FROM AUTHOR]

Materials with perovskite structure are known to exhibit fascinating physical properties such as high-temperature superconductivity, negative thermal expansion (NTE) and colossal magnetoresistance. However, transition metal trifluoride perovskites are less well studied compared to their oxide counterparts though they display marked differences such as NTE behavior in ScF3. Doping of such MF3 perovskites has been the focus of the experimental work of Morelock et al. [1] which provides a comprehensive structural study of the material class Sc1 − x Ti x F3. As shown in Fig. 1, there is a structural phase transition assumed to be tied to tilting of corner sharing octahedrons in this class of crystal structures which is believed to have an electrostatic dipolar origin, seen for example even in AlF3 [2]. However, the insulating and magnetic properties of TiF3 are closely related to the transition metal 3d-electrons. The extra valence d -electron that Ti carries compared to Sc [1, 3] gives rise to unusual electronic and magnetic properties. [ABSTRACT FROM AUTHOR]

Materials with perovskite structure are known to exhibit fascinating physical properties such as high-temperature superconductivity, negative thermal expansion (NTE) and colossal magnetoresistance. However, transition metal trifluoride perovskites are less well studied compared to their oxide counterparts though they display marked differences such as NTE behavior in ScF3. Doping of such MF3 perovskites has been the focus of the experimental work of Morelock et al. [1] which provides a comprehensive structural study of the material class Sc1 − x Ti x F3. As shown in Fig. 1, there is a structural phase transition assumed to be tied to tilting of corner sharing octahedrons in this class of crystal structures which is believed to have an electrostatic dipolar origin, seen for example even in AlF3 [2]. However, the insulating and magnetic properties of TiF3 are closely related to the transition metal 3d-electrons. The extra valence d -electron that Ti carries compared to Sc [1, 3] gives rise to unusual electronic and magnetic properties. [ABSTRACT FROM AUTHOR]

High entropy rare earth silicate ceramics have been widely studied as potential material for environmental barrier coatings (EBCs). At present, the synthesis method of high entropy rare earth silicate ceramics is generally solid state reaction method, which has some problems such as high energy consumption, low efficiency and low purity of synthesized products. In order to solve these problems, high entropy (Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2) 2 SiO 5 was prepared by molten salt synthesis (MSS). By adjusting the reaction temperature and the amount of molten salt, it was found that the pure high entropy (Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2) 2 SiO 5 ceramic powders could be synthesized at 1400 °C when Na 2 SO 4 and K 2 SO 4 are selected as molten salts(Na+:K+ = 1:1), and the mass ratio of molten salt to reactant is 1: 1. The molten salt synthesis significantly reduced the reaction temperature and accelerated the reaction rate. The prepared high entropy (Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2) 2 SiO 5 has a monoclinic X 2 -type Re 2 SiO 5 structure and a low thermal conductivity of 0.96 ± 0.03 W m-1 K-1 due to the high entropy effect. This can be explained by the existence of high concentration oxygen vacancies and the highly disordered arrangement of multicomponent cations in a unique high entropy configuration. This material also shows good infrared reflectance, which makes (Y 0.2 Sm 0.2 Eu 0.2 Er 0.2 Yb 0.2) 2 SiO 5 a potential environmental barrier coating material. [ABSTRACT FROM AUTHOR]

The increasing attention towards wearable materials with excellent thermal insulation properties stems from their potential to save energy and fulfill the requirement for smart clothing, thereby addressing the fundamental need to maintain human body temperature. In this work, the multifunctional Cu nanoparticles/cellulose fibers aerogels (Cu-NPs/CFAs) composites with functional integration were prepared via simple in-situ deposition and freeze-drying process using sisal cellulose as starting material for thermal insulation applications. During this process, sisal cellulose was extracted to obtain cellulose aerogel, which was then in-situ deposited with copper nanoparticles through redox reactions. The subsequent freeze drying resulted in the formation of porous Cu-NPs/CFAs with high infrared reflection and self-cleaning properties. The SEM images showed that the Cu nanoparticles were tightly anchored on surface of cellulose aerogel, forming the high infrared reflection coating. The reflectivity of copper nanoparticle coating is approximately 0.85 to 0.95 in the ranging from 2 to 14 μm, indicating the high thermal insulation for human warmth in the cold environment. Besides, obtained Cu-NPs/CFAs material shows a self-cleaning property with a stable water contact angle of 150.5°, which can provide a stable infrared performance on the surface of the material. The present results indicate that Cu-NPs/CFAs are promising candidates as insulation material for human thermal management, energy regulation and other facility applications. Highlights: Aerogel composites were fabricated using sisal cellulose as starting material. Copper nanoparticles had been successfully deposited on the surface of the CFAs. Aerogel composites have a high infrared reflectivity. Cu-NPs/CFAs showed excellent stable hydrophobic performance. Cu-NPs/CFAs are promising candidates as insulation material for thermal management application. [ABSTRACT FROM AUTHOR]

The optical properties of the ZnGa2Se4 are investigated by infrared (IR) reflectivity, Raman scattering, photoluminescence and DFT simulations. We have analyzed pairs of lines of FL corresponding to 1.24 eV and 1.22 eV at low energy excitations, about these FL maxima haven't any information in other works. Studies show that depending on the temperature, the intensity of luminescence decreases and formed new third maximum. The energy difference between each of these peaks is 0.02 eV, which corresponds to the energy of the most intense phonon in the Raman spectrum. [ABSTRACT FROM AUTHOR]

The optical properties of the ZnGa2Se4 are investigated by infrared (IR) reflectivity, Raman scattering, photoluminescence and DFT simulations. We have analyzed pairs of lines of FL corresponding to 1.24 eV and 1.22 eV at low energy excitations, about these FL maxima haven't any information in other works. Studies show that depending on the temperature, the intensity of luminescence decreases and formed new third maximum. The energy difference between each of these peaks is 0.02 eV, which corresponds to the energy of the most intense phonon in the Raman spectrum. [ABSTRACT FROM AUTHOR]

The lattice dynamical properties of dilute InAs1−xNx/InP (001) epilayers (0 ≤ x ≤ 0.03) grown by gas-source molecular beam epitaxy were carefully studied experimentally and theoretically. A high-resolution Brüker IFS 120 v/S spectrometer was employed to measure the room-temperature infrared reflectivity (IRR) spectra at near-normal incidence (θi = 0). The results in the frequency range of 180–500 cm−1 revealed accurate values of the characteristic In-As-like and In-N-like vibrational modes. For InAs1−xNx alloys, a classical "Drude–Lorentz" model was constructed to obtain the dielectric functions ε ~ ω in the far IR regions by incorporating InAs-like and InN-like transverse optical ω T O modes. Longitudinal optical ω L O phonons were achieved from the imaginary parts of the simulated dielectric loss functions. The theoretical results of IRR spectra for InAs1−xNx/InP (001) epilayers using a multi-layer optics methodology provided a very good agreement with the experimental data. At oblique incidence (θi ≠ 0), our study of s- and p-polarized reflectance (Rs,p(ω)) and transmission (Ts,p(ω)) spectra allowed the simultaneous perception of the ω T O and ω L O phonons of the InAs, InN and InAs0.97N0.03 layers. Based on the average t-matrix Green's function theory, the results of local vibrational modes for light S i I n + donors and S i A s − ,   C A s − acceptors in InAs were found in good agreement with the existing Raman scattering and infrared spectroscopy data. I n I n N , however, the method predicted an in-band mode for the M g I n − acceptor while projecting an impurity mode of the S i I n + donor to appear just above the maximum ω m a x I n N [ ≡ 595   c m − 1 ] phonon frequency region. In InAs1−xNx/InP (001) epifilms, the comparison of reflectivity/transmission spectra with experiments and the predictions of impurity modes for isoelectronic donor and acceptor impurities in InAs and InN can be valuable for appraising the role of defects in other technologically important semiconductors. [ABSTRACT FROM AUTHOR]

The detection and classification of microplastics in the marine environment is a complex task that implies the use of delicate and expensive instrumentation. In this paper, we present a preliminary feasibility study for the development of a low-cost, compact microplastics sensor that could be mounted, in principle, on a float of drifters, for the monitoring of large marine surfaces. The preliminary results of the study indicate that a simple sensor equipped with three infrared-sensitive photodiodes can reach classification accuracies around 90% for the most-diffused floating microplastics in the marine environment (polyethylene and polypropylene). [ABSTRACT FROM AUTHOR]

Temperature stable xLi 2 MoO 4 -(1-x)(LiBi) 0.5 MoO 4 (x = 0, 40, 50, 60, 70, 100 vol%) microwave dielectric ceramics obtained by cold sintering process (CSP) under a mild sintering condition (120 ℃/30 min/200 MPa) are introduced in this work. The XRD, SEM, and Raman analysis indicate the coexistence of Li 2 MoO 4 and (LiBi) 0.5 MoO 4 phases. Li 2 MoO 4 -(LiBi) 0.5 MoO 4 ceramics are compatible with Ag and Al electrode materials under cold sintering condition. The specimens exhibit high relative densities and good microwave dielectric properties (relative permittivities: 31.5–5.5; Q×f values: 1900 - 18,500 GHz; TCF values: from +144 ppm/℃ to −106 ppm/℃), in particular, TCF = +0.7 ppm/℃ can be obtained in the case of x = 50 vol%. The extrapolated microwave dielectric properties obtained by the fitted infrared reflectivity spectrum are close to the measured data, revealing that the dielectric responses of cold sintered Li 2 MoO 4 -(LiBi) 0.5 MoO 4 ceramics in the microwave range are dominated by the polar optical phonons. [ABSTRACT FROM AUTHOR]

The lattice dynamical properties of dilute InAs1−xNx/InP (001) epilayers (0 ≤ x ≤ 0.03) grown by gas-source molecular beam epitaxy were carefully studied experimentally and theoretically. A high-resolution Brüker IFS 120 v/S spectrometer was employed to measure the room-temperature infrared reflectivity (IRR) spectra at near-normal incidence (θi = 0). The results in the frequency range of 180–500 cm−1 revealed accurate values of the characteristic In-As-like and In-N-like vibrational modes. For InAs1−xNx alloys, a classical “Drude–Lorentz” model was constructed to obtain the dielectric functions ε~ω in the far IR regions by incorporating InAs-like and InN-like transverse optical ωTO modes. Longitudinal optical ωLO phonons were achieved from the imaginary parts of the simulated dielectric loss functions. The theoretical results of IRR spectra for InAs1−xNx/InP (001) epilayers using a multi-layer optics methodology provided a very good agreement with the experimental data. At oblique incidence (θi ≠ 0), our study of s- and p-polarized reflectance (Rs,p(ω)) and transmission (Ts,p(ω)) spectra allowed the simultaneous perception of the ωTO and ωLO phonons of the InAs, InN and InAs0.97N0.03 layers. Based on the average t-matrix Green’s function theory, the results of local vibrational modes for light SiIn+ donors and SiAs−, CAs− acceptors in InAs were found in good agreement with the existing Raman scattering and infrared spectroscopy data. InInN, however, the method predicted an in-band mode for the MgIn− acceptor while projecting an impurity mode of the SiIn+ donor to appear just above the maximum ωmaxInN[≡595 cm−1] phonon frequency region. In InAs1−xNx/InP (001) epifilms, the comparison of reflectivity/transmission spectra with experiments and the predictions of impurity modes for isoelectronic donor and acceptor impurities in InAs and InN can be valuable for appraising the role of defects in other technologically important semiconductors.

A series of double-perovskite La2Co1−zFezMnO6 (z = 0, 0.2–1.0) ceramics were synthesized using a well-established sol–gel method. The series of samples with a monoclinic phase and a P21/n symmetry were characterized by XRD, FTIR, conductivity, and capacitance measurement to extract charge-transport and dielectric characteristics at room temperature. The obtained IR spectra fitted well with the Lorentz oscillator model to calculate the damping factor, optical frequency, and oscillator strength and compared with the theory, which gave better agreement. The calculated activation energies from the Arrhenius plot supported the semiconducting nature of all samples. The temperature and frequency-dependent dielectric parameters, such as the real part ( ε r ′ ), imaginary part ( ε ″ ) of the dielectric constant, dielectric loss (tanδ), and ac-conductivity (σac) were extracted. The dielectric constant ( ε r ′ ,     ε ″ ) and dielectric loss (tanδ) were enhanced at a low frequency, while the ac-conductivity (σac) displayed higher values at higher frequencies. The enhancement in the dielectric parameters with increasing iron concentrations arose due to the higher surface volume fraction of iron (Fe3+) ions than the cobalt (Co3+) ions. The radius of the Fe3+ (0.645 Å) was relatively higher than the Co3+ ions (0.61 Å), significantly influenced by the grains and grain boundaries, and enhanced the barrier for charge mobility at the grain boundaries that play a vital role in space charge polarization. [ABSTRACT FROM AUTHOR]

Infrared physical properties of single crystal A1 3 BC 3. [Display omitted] • The dielectric and infrared properties of single crystal Al 3 BC 3 were first calculated using density functional perturbation theory. • All infrared-active modes at the Brillouin zone center were identified for single crystal Al 3 BC 3. • There were stronger covalent bonds between B-C and ionic bonds between Al-C in Al 3 BC 3 ceramics. The dielectric and infrared vibrational properties of single crystal Al 3 BC 3 were computed using density functional perturbation theory. Utilizing a group theory approach, the frequencies and vibrational modes of all the infrared active modes at the Brillouin zone center were determined. The study explored the dielectric function, infrared reflectivity, and Born effective charge of Al 3 BC 3 in directions both parallel and perpendicular to the c -axis. The analysis of the Born effective charge confirmed the existence of strong covalent bonds between B and C, as well as ionic bonds between Al and C in Al 3 BC 3 ceramics. [ABSTRACT FROM AUTHOR]

The detection and classification of microplastics in the marine environment is a complex task that implies the use of delicate and expensive instrumentation. In this paper, we present a preliminary feasibility study for the development of a low-cost, compact microplastics sensor that could be mounted, in principle, on a float of drifters, for the monitoring of large marine surfaces. The preliminary results of the study indicate that a simple sensor equipped with three infrared-sensitive photodiodes can reach classification accuracies around 90% for the most-diffused floating microplastics in the marine environment (polyethylene and polypropylene).

The K 0.5 Na 0.5 NbO 3 (KNN) system has emerged as one of the most promising lead-free piezoelectric over the years. In this work, we perform a comprehensive investigation of electronic structure, lattice dynamics and dielectric properties of room temperature phase of KNN by combining ab-initio DFT based theoretical analysis and experimental characterization. We assign the symmetry labels to KNN vibrational modes and obtain ab-initio polarized Raman spectra, Infrared reflectivity, Born-effective charge tensors, oscillator strengths etc. The KNN ceramic samples are prepared using conventional solid-state method and Raman and UV-Vis diffuse reflectance spectra are obtained. The computed Raman spectrum is found to agree well with the experimental spectrum. In particular, the results suggest that the mode in range ∼840-870 cm -1 reported in the experimental studies is longitudinal optical withA1symmetry. The Raman mode intensities are calculated for different light polarization set-ups that suggests the observation of different symmetry modes in different polarization set-ups. The electronic structure of KNN is investigated and optical absorption spectrum is obtained. Further, the performances of DFT semi-local, meta-GGA and hybrid exchange-correlations functionals, in the estimation of KNN band gaps are investigated. The KNN bandgap computed using GGA-1/2 and HSE06 hybrid functional schemes are found to be in excellent agreement with the experimental value. The COHP, electron localization function and Bader charge analysis is also performed to deduce the nature of chemical bonding in the KNN. Overall, our study provides several bench-mark important results on KNN that have not been reported so far., (© 2024 IOP Publishing Ltd.)

The polycrystalline NdMn2O5 multiferroic was synthesized by wet chemistry method followed by heat treatment at 1000 °C. The structure was confirmed by X-ray diffraction (XRD) as orthorhombic with space group Pbam. The particle size and strain were calculated by Williamson-Hall method. Both infrared (IR) active and Raman active phonons have been observed using IR reflectivity and Raman spectroscopies. UV–visible absorption spectrum suggests that a possible optical band Eg ∼ 1.27 eV has been determined using Kubelka–Munk function. Magnetic field (2 T) dependent magnetization at room temperature suggests the paramagnetic nature of present compound. In addition, frequency-dependent dielectric properties (20Hz–30 GHz) indicate variation in dielectric constant, dielectric loss, tangent loss, as well as AC conductivity, in two distinct dielectric responses which are in accord with Debye relaxation model. [ABSTRACT FROM AUTHOR]

In this study, Ce 1−x Cu x O 2−x (x = 0, 0.01, 0.03, 0.05, 0.07) samples were prepared by hydrothermal method. The structure, microstructure, and elemental composition of the powders were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, whereas the electrical conductivity, ultraviolet–visible absorption spectroscopy, and infrared emissivity at 3–5 μm were measured as well. Moreover, the effects of Cu2+ doping concentration on the microstructure, morphology, bandgap, conductivity, and infrared emissivity of Cu-doped CeO 2 powders were systematically studied. The effects of Cu2+ doping on infrared reflection and absorption in a 3–5 μm band and their mechanisms were explained based on electromagnetic theory, lattice vibration absorption, and free carrier absorption. Our result indicated that the emissivity of 1% Cu-doped powder reached the lowest emissivity of 0.200 at 800 °C. When the doping concentration was above 1%, the curve of infrared emissivity versus temperature exhibited a "U" shape, with the minimum point shifting towards the low-temperature region with the increase of Cu doping amount. This phenomenon was attributed to the different enhancement amplitude of reflectivity and absorbance of CeO 2 powder by Cu2+ at different temperatures. [ABSTRACT FROM AUTHOR]

The Ca 3 M 2 Si 3 O 12 (M = Yb, Y) ceramics with orthorhombic silico-carnotite structure were fabricated via high-energy ball milling and solid-state reaction route. Dense Ca 3 Yb 2 Si 3 O 12 and Ca 3 Y 2 Si 3 O 12 ceramics sintered at 1260 °C and 1240 °C revealed promising microwave dielectric properties with ε r = 9.2 and 8.7, Q×f = 56,400 GHz and 29,094 GHz, τ f = −77.5 ppm/°C and −76.8 ppm/°C, respectively. The connection between crystal structure and Q×f values of Ca 3 M 2 Si 3 O 12 (M = Yb, Y) ceramics was discussed with respect to the packing fraction, and their intrinsic microwave dielectric properties were examined using the infrared reflectivity spectra analysis. The thermal stability of Ca 3 Yb 2 Si 3 O 12 was improved successfully by forming 0.91Ca 3 Yb 2 Si 3 O 12 ‐0.09CaTiO 3 composite ceramics with τ f = +2.9 ppm/°C, ε r = 12.93 and Q×f = 26,729 GHz. [ABSTRACT FROM AUTHOR]

This paper systematically investigated the influence of Ti4+ substitution for Ta5+ on the phase composition and microwave dielectric properties of Ba 3 Ta 4-4x Ti 4+5x O 21 (x = 0.1, 0.2, and 0.3) ceramics with hexagonal tungsten bronze-like structures. X-ray diffraction and Rietveld refinement results indicated that single-phase Ba 3 Ta 4 Ti 4 O 21 could be obtained only with the x values of 0.1 and 0.2, and a secondary phase was detected at an x value of 0.3. The valence state of Ba 3 Ta 4-4x Ti 4+5x O 21 (x = 0.2) ceramics was analyzed through X-ray photoelectron spectroscopy. Increasing Ti4+/Ta5+ ratios could reduce sintering temperature and improve the microwave dielectric properties of Ba 3 Ta 4-4x Ti 4+5x O 21 solid solutions. However, the dielectric properties, particularly the quality factor, of Ba 3 Ta 4-4x Ti 4+5x O 21 ceramics deteriorated severely as a result of oxygen vacancy defects caused by the transition of the valence state from Ti4+ to Ti3+ when x = 0.2 and the coexistence of the secondary phase when x = 0.3. Infrared reflectivity spectroscopy was performed to explore the intrinsic dielectric properties of Ba 3 Ta 4-4x Ti 4+5x O 21 (x = 0.1) ceramics. The measured and extrapolated microwave dielectric properties of Ba 3 Ta 4-4x Ti 4+5x O 21 (x = 0.1) ceramics sintered at 1240 °C for 6 h were ε r ~ 46.5, Q × f = 13,900 GHz, τ f ~ +49.4 ppm/°C, and ε r ~ 44, Q × f = 34,850 GHz. [ABSTRACT FROM AUTHOR]

Multiferroic manganite La1-xYxMnO3 (LYMO) (x=0.0, 0.2, 0.4, 0.6) have been synthesized by using sol-gel method. The powder X-ray diffraction (XRD) pattern with a Rietveld refinement analysis exhibits a transition from rhombohedral to orthrohombic for 0.4 ≤ x ≤ 0.6. A comprehensive study of infrared (IR) active phonons was carried out at room temperature in the frequency range 30-7500 cm-1 by means of Fourier transform infrared (FTIR) spectrometer. Optical parameters i.e. resonant frequency (ωTO(j)), oscillator strength (Sj) and damping factor (Υj) of observed phonons have been determined by Lorentz oscillators model fit to the measured reflectivity. The frequency shifts of optical phonons have been observed with the increase in x. The change in optical parameters of IR active phonons reflects the confirmation of phase transformation. Moreover, Born and Szigeti effective charges were calculated to understand the polarization effect and ionicity in the present multiferroic system. [ABSTRACT FROM AUTHOR]

The infrared reflectivity spectra for potassium-doped polycrystalline magnesium aluminates MgKAl2O4 ( x=0, 0.25, 0.50, 0.75, 1) are measured in the frequency range between 10-15, 500 cm 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 MgKAl2O4, 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 (()) and found to be x dependent. [ABSTRACT FROM AUTHOR]

Comprehensive experimental and theoretical studies are reported to assess the vibrational and structural properties of 3C-SiC/Si (001) epilayers grown by chemical vapor deposition in a vertical reactor configuration. While the phonon features are evaluated using high resolution infrared reflectance (IRR) and Raman scattering spectroscopy (RSS) – the local inter-atomic structure is appraised by synchrotron radiation extended x-ray absorption fine structure (SR-EXAFS) method. Unlike others, our RSS results in the near backscattering geometry revealed markedly indistinctive longitudinal- and transverse-optical phonons in 3C-SiC epifilms of thickness d < 0.4 μm. The estimated average value of biaxial stress is found to be an order of magnitude smaller while the strains are two-orders of magnitude lower than the lattice misfits between 3C-SiC and Si bulk crystals. Bruggeman’s effective medium theory is utilized to explain the observed atypical IRR spectra in 3C-SiC/Si (001) epifilms. High density intrinsic defects present in films and/or epilayer/substrate interface are likely to be responsible for ( a ) releasing misfit stress/strains, ( b ) triggering atypical features in IRR spectra, and ( c ) affecting observed local structural traits in SR-EXAFS. [ABSTRACT FROM AUTHOR]

Infrared reflectivity spectra are measured in the frequency range between 10 and 15,500 cm −1 at room temperature for cobalt substituted nanocrystalline magnesium aluminates MgAl 2− x Co x O 4 ( x = 0.0, 0.5, 1.0, 1.5, 2.0). Four optical phonon modes manifesting the spinel structure have been observed and analyzed using the Lorentz oscillator model. The resonant frequency, oscillator strength and the damping factor of these modes were extracted from Lorentz oscillator fit to measured spectra. The observed reflectivity spectra exhibit a typical semiconductor behavior. Born and Szigeti effective charges have been estimated and the results are discussed to understand polarization and ionicity of MgAl 2− x Co x O 4 system. [ABSTRACT FROM AUTHOR]

A systematic investigation of infrared active phonon excitations in the orthorhombic Dy 1 - x Y x Mn 2 O 5 with x =0, 0.2, 0.4, 0.6, 0.8, and 1 was carried out at room temperature. A detailed analysis towards the correlation between both local structural response and local lattice distortion has been undertaken. Frequency shifts of several phonons were observed, which strongly depends on the Y concentration and are likely to be associated with the electron–phonon coupling. A strong evidence for structural distortions of MnO 6 and MnO 5 has been observed in the high frequency range. The optical band gap has also been determined through optical conductivity and UV-visible absorption spectra, indicating semiconducting behavior of all members of the series Dy 1 - x Y x Mn 2 O 5 . [ABSTRACT FROM AUTHOR]

Room-temperature infrared (IR) reflectivity, terahertz transmission and evaluated effective complex dielectric response of four polycrystalline alumina ceramics (corundum) with highly anisotropic grains in the IR range were determined. The spectra were compared with modelled spectra based on the known IR response of sapphire single crystal and Bruggeman and Lichtenecker models of the effective medium approximation (EMA). The results are extremely sensitive to the surface treatment (polishing), but do not depend on the grain size in the range of ∼0.3-1 μm and on the weak doping, needed for processing of optically transparent ceramics. As all the samples show similar grain shapes and topology, no measurable differences among the fully dense samples were observed. Agreement with the modelled spectra is reasonable, but shows a higher effective mode damping. A weak geometrical resonance was revealed near 500 cm−1, better described by the Bruggeman model. The small sample porosity up to 6.2% is revealed mainly as a reduced reflectivity above ∼650 cm−1, which produces weak losses in the high-frequency range above the TO phonon modes, better described by the Lichtenecker model. [ABSTRACT FROM AUTHOR]

Lanthanide orthotantalates Ln TaO 4 (Ln = La, Nd, Dy and Lu) were synthesized by solid-state reactions at 1300 °C leading to well crystallized single-phase materials. XRD and infrared spectroscopic investigations showed that the samples exhibited three different monoclinic crystal structures depending on the lanthanide ion: P 2 1 / c (for La), I2/a (for Nd) and P2/a (for Dy and Lu). For LaTaO 4 , 21 polar modes could be depicted from the unpolarized infrared reflectivity spectrum, while group theory tools foreseen 33 infrared-active modes – the absent mode are likely hidden by accidental degeneracy. The smaller lanthanides (Nd, Dy and Lu) exhibited all the 15 predicted infrared-active bands, in perfect agreement with group-theory calculations, despite the mixing of polarization symmetry due to the polycrystalline nature of the samples. The intrinsic (infrared) dielectric properties were determined for all samples indicating that these orthotantalate ceramics could be candidates for microwave (MW) circuitry applications. LaTaO 4 ceramics exhibited the best MW dielectric response among the investigated Ln TaO 4 ( ɛ r = 21.2 and estimated Q u × f ≈ 77 THz), followed by DyTaO 4 ( ɛ r = 19.9 and Q u × f ≈ 75 THz), NdTaO 4 ( ɛ r = 18.7 and Q u × f ≈ 55 THz), and LuTaO 4 ( ɛ r = 16.2 and Q u × f ≈ 60 THz). [ABSTRACT FROM AUTHOR]

The far-and mid-infrared reflectivity spectra of two carbon layers deposited on pure (100) silicon substrates by DC magnetron sputtering were investigated at room temperature in the 10–5000 cm −1 wavenumber range. Their structural and textural features were also studied by combining Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray Reflectivity (XRR) and Rutherford Backscattering Spectroscopy (RBS). The set of results was used to discuss afterwards the influence of the texture on the infrared properties at varying length scale. Thereby, the two layers were found to be heterogeneous as assessed by RBS, XRR and FESEM and their thicknesses had been measured by XRR and FESEM. The information on the structural organization and “crystallite” size was given by Raman spectroscopy. The influence of both the textural and structural parameters on the measured infrared reflectivity spectra was discussed. Finally, a methodology was proposed to recover the intrinsic index of refraction and the intrinsic index of absorption of each layer. [ABSTRACT FROM AUTHOR]

• Laminated CMPFA membranes were fabricated via electrospinning, vacuum filtration, and magnetron sputtering. • Waster polyester clothes were used to fabricate substrate membranes. • The asymmetrically wettable improve sweat transportation properties of CMPFA membranes. • Laminated CMPFA membranes can reflect thermal radiation and absorb solar energy to achieve dual thermal insulation. • The obtained CMPFA membranes have potential application in human thermal management. Wearable polyester fiber materials with excellent sweat transportation and enhanced thermal management properties have received increasing attention in functional materials and energy saving fields because of not only for wearing comfort but also for developing advanced energy-saving materials. Herein, this work presents an effective and sustainable strategy for fabrication of laminated CNTs-MnO 2 nanowires/PET fibers@Ag (CMPFA) membranes using waste polyethylene terephthalate (PET) fabric, manganese dioxide (MnO 2) nanowires, carbon nanotubes (CNTs) and silver nanoparticles as building blocks through electrospinning, vacuum filtration and subsequent magnetron sputtering processes, as well as its application in personal thermal management. The results indicated that simulated sweat on the PET fibers@Ag side can penetrate quickly into the CNTs-MnO 2 nanowires side within 2.4 s, implying the excellent sweat transport properties of laminated CMPFA membranes. More importantly, the synergistic thermal management properties can be obtained via infrared radiation and absorb sunlight. Compared with bare PET fibers membranes, the laminated CMPFA membranes exhibited excellent thermal insulation properties. The surface temperature of laminated CMPFA membranes is 11.9 °C higher than that of bare PET fibers membranes after 50 s of simulate sunlight exposure. In addition, the laminated CMPFA membranes show antibacterial properties, breathability, and water vapor permeability, which is beneficial to improving the comfort of wearer. This study shows that the fabrication of flexible wearable laminated membranes for personal thermal management application can be extended for the fabricated of other waste plastic based-materials with controlled structures and desired functions for various applications. [ABSTRACT FROM AUTHOR]

Far infrared spectra of sintered PbTe doped with boron were analyzed. The measured infrared spectra were fitted using a modified plasmon-phonnon interaction model with two additional oscillators (at about 195 cm-1 and 285 cm-1) representing local B-impurity modes. The obtained results were compared with previously published data for a single crystal PbTe sample doped with boron.

The perovskite structure manganese oxides La 0.67 Ca 0.33−x Sr x MnO 3 (x = 0, 0.03, 0.05, 0.08, 0.10, 0.13, 0.15) were synthesized by conventional solid-state reaction. The crystal structure, temperature-dependent electrical resistance and infrared reflectivity as well as total hemispherical emissivity properties of the prepared compounds were systematically investigated. The results indicate that all doped compounds have obvious metal-insulator transition when the temperature increases in a certain range. When the doping level x is equal to 0.03, 0.05 or 0.08, the metal-insulator transition temperature can be adjusted to 0 °C–10 °C and the variation of total hemispherical emissivity exceeds 0.45 ranging from −50 °C to +50 °C. All the properties mentioned above enable the compounds to show large application prospects on the thermal control systems of satellites. [ABSTRACT FROM AUTHOR]

In this letter we discuss experimental results on optical reflectance of ultrathin metallic films. The laser light source was tuned at the infrared wavelength of λ = 9.2 μ m . Three metals were tested: aluminum, niobium, and nickel. The thin films were coated on various wafers, namely, fused glass, α-quartz and amorphous silicon, with the technique of magnetic field assisted sputtering modulated at radio frequencies. The infrared reflectance was recorded while the thickness of the film varied from 5 to little more than 100 Å. A phenomenon is observed, i.e. a periodic oscillation appeared modulated on the otherwise classic thickness dependence of metallic films. The effects are attributed to the influence of quantum confinement induced intraband redistribution of conduction electrons. A one-dimensional quantum well model was employed to simulate the system, and the numerical results confirmed the existence of the quantum size effect. [ABSTRACT FROM AUTHOR]

The infrared (IR) reflectivity of laser synthesized TiO2 nanopowder in the anatase phase with a small deviation from stoichiometry is reported. The samples were characterized by SEM, XRD and BET measurements as well as Raman and photoluminescence spectroscopy. Analysis of the far IR reflectivity spectrum of the nanopowder reveals a presence of a plasmon mode. The charge carriers resulting from the lattice defects, mainly oxygen vacancies, are responsible for this mode. The dielectric function in a factorized form with a plasmon contribution is used to model the IR reflectivity spectrum and a good agreement between theoretical and experimental results has been found.

The Raman, infrared reflectivity and terahertz spectra of A-site deficient scheelite materials (Ca 1−3 x Bi 2 x Φ x )MoO 4 (Φ: A-site vacancy) were studied to evaluate the correlation between the vibrational modes and the dielectric properties. The Raman spectra were fitted with the Lorentzian model and the changes of resonance frequencies and full width at half maximum of the resonance were discussed. With the substitution of Bi into the A site of CaMoO 4 , the associated ionic compensation produces an increase in disorder which can contribute to an increase in dielectric losses. The harmonic oscillator model was used to fit infrared reflectivity spectra and the obtained complex dielectric response was extrapolated down into the terahertz and microwave region. The contributions of each mode to the microwave dielectric properties were investigated. It was found that the modes at low frequencies which are related to AO 8 polyhedra play the most important role in the microwave dielectric properties of (Ca 1−3 x Bi 2 x Φ x )MoO 4 . [ABSTRACT FROM AUTHOR]

Abstract: Raman scattering and infrared reflectivity performed on polycrystalline SmCrO3 support strong influence of the antiferromagnetic order on phonon modes. Both measurements show softening of some modes below T N . Such a behavior is explained by spin–phonon coupling in this compound. Furthermore, temperature dependence of the infrared spectra has demonstrated important changes compared to the Raman spectra, suggesting strong structural modifications due to the cation displacements rather to those of the oxygen ions. Our results reveal that polar distortions originating in local symmetry breaking, i.e. local non-centrosymmetry, resulting in Cr off-centring. [Copyright &y& Elsevier]

Abstract: Sea surface infrared reflectivity is an important parameter in oceanic remote sensing. Most analytical models consider single surface reflections, and the polarization is usually ignored. However, a loss of energy is reported for large observation angles (θ >50°) because multiple surface reflections are ignored. This article generalizes the infrared reflectivity derivation of Li et al. (Appl. Opt., Vol. 52, 6100–6111, 2013) for 1D surfaces (2D problems) to 2D surfaces (3D problems), so that the cross-polarization effect can be taken into account. The contributions of one and two successive surface reflections are analyzed separately. The bidirectional reflectivity and the hemispherical reflectivity are studied. It is shown that the sea surface infrared reflectivity is significant for large incidence and observation angles. The energy conservation criterion is then checked. The loss of energy is largely reduced after taking into account two surface reflections. [Copyright &y& Elsevier]

Abstract: We report growth of large single crystals of β-BaTeMo2O9, and single crystal infrared (IR) reflectance spectra as well as polarized Raman spectra for these crystals. Based on these results, the symmetry and LO–TO splitting have been established for the observed modes. We also propose assignment of the observed modes to the respective vibrations of structural units. [Copyright &y& Elsevier]

Abstract: The infrared and nonresonant Raman spectra of YF3 have been studied within the framework of density functional perturbation theory. We report the calculated frequencies of three Raman active modes and one IR active mode that could not be detected experimentally. The valence and conduction band structure of YF3 have been calculated, using density functional theory. A good agreement between the calculated valence band width and experimental result was obtained, and an indirect energy gap of 7.58eV is estimated in the local density approximation. [Copyright &y& Elsevier]

Abstract: Temperature dependent normal modes and lattice thermal expansion of Sr2 B′UO6 (B′=Ni, Co) double perovskites were investigated by Raman/infrared spectroscopies and synchrotron X-ray diffraction, respectively. Monoclinic crystal structures with space group P2 1 /n were confirmed for both compounds, with no clear structural phase transition between 10 and 400K. As predicted for this structure, the first-order Raman and infrared spectra show a plethora of active modes. In addition, the Raman spectra reveal an enhancement of the integrated area of an oxygen stretching mode, which is also observed in higher-order Raman modes, and an anomalous softening of ∼1cm−1 upon cooling below T* ∼300K. In contrast, the infrared spectra show conventional temperature dependence. The band profile phonon anomalies are possibly related to an unspecified electronic property of Sr2 B′UO6 (B′=Ni, Co). [ABSTRACT FROM AUTHOR]

We report on the experimental and theoretical study of the lattice dynamics in Ba0.7Sr0.3TiO3 in 20-900 K temperature range. Complex dielectric response in the terahertz and far infrared range was evaluated from the time-domain THz transmission spectra and infrared reflectivity by means of damped harmonic oscillator models in classical and factorized form of the dielectric function. The anisotropic dielectric function in the ferroelectric phases was extracted using the Bruggeman model of the effective medium approximation. The fitted parameters of the temperature-dependent Slater-type vibrations (soft mode and central mode, CM) were compared with those obtained from ab initio simulations. The role of the lattice phonons and CM in the dielectric anomaly is discussed. [ABSTRACT FROM AUTHOR]