The synthesis of narrow-band red-emitting SrLiAl3N4:Eu2+phosphor and improvement of its luminescence properties

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

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Temperature Dependent Line-Shape of the Silicon Dangling Bond EPR-Resonance in Polycrystalline Silicon

MRS Proceedings ◽

10.1557/proc-452-1019 ◽

1996 ◽

Vol 452 ◽

Cited By ~ 1

Author(s):

N. H. Nickel ◽

E. A. Schiff

Keyword(s):

Electron Paramagnetic Resonance ◽

Polycrystalline Silicon ◽

Room Temperature ◽

Dangling Bond ◽

Temperature Dependent ◽

Paramagnetic Resonance ◽

Temperature Electron ◽

Motional Narrowing ◽

G Value ◽

Electron Paramagnetic

AbstractThe temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropie g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔHpp. In unpassivated poly-Si a pronounced decrease of ΔHpp is observed for temperatures above 300 K. At 384 K ΔHpp reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔHpp decreases monotonically above 425 K. The decrease of ΔHpp is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 Å was estimated for unhydrogenated and H passivated poly-Si, respectively.

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Thermochromic aggregation-induced dual phosphorescence via temperature-dependent sp3-linked donor-acceptor electronic coupling

Nature Communications ◽

10.1038/s41467-021-21676-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Tao Wang ◽

Zhubin Hu ◽

Xiancheng Nie ◽

Linkun Huang ◽

Miao Hui ◽

...

Keyword(s):

Excited State ◽

Room Temperature ◽

Electronic Coupling ◽

Temperature Dependent ◽

Molecular Systems ◽

Donor And Acceptor ◽

Theoretical Investigations ◽

Donor Acceptor ◽

And Control ◽

Two Temperature

AbstractAggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, we show that by utilizing triphenylamine (TPA) as an electronic donor that connects to an acceptor via an sp3 linker, six TPA-based AIE-active RTP luminophores were obtained. Distinct dual phosphorescence bands emitting from largely localized donor and acceptor triplet emitting states could be recorded at lowered temperatures; at room temperature, only a merged RTP band is present. Theoretical investigations reveal that the two temperature-dependent phosphorescence bands both originate from local/global minima from the lowest triplet excited state (T1). The reported molecular construct serves as an intermediary case between a fully conjugated donor-acceptor system and a donor/acceptor binary mix, which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics.

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Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

Scientific Reports ◽

10.1038/s41598-021-96299-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Aastha Vasdev ◽

Moinak Dutta ◽

Shivam Mishra ◽

Veerpal Kaur ◽

Harleen Kaur ◽

...

Keyword(s):

Thermal Conductivity ◽

Figure Of Merit ◽

Room Temperature ◽

Lattice Thermal Conductivity ◽

Direct Evidence ◽

Temperature Dependent ◽

Force Microscopy ◽

Ferroelectric Domains ◽

Pdf Analysis ◽

Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

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Atomistic prediction on the configuration- and temperature-dependent dielectric constant of Be0.25Mg0.75O superlattice as a high-κ dielectric layer

Journal of Materials Chemistry C ◽

10.1039/d0tc05071g ◽

2021 ◽

Author(s):

Gyuseung Han ◽

In Won Yeu ◽

Kun Hee Ye ◽

Seung-Cheol Lee ◽

Cheol Seong Hwang ◽

...

Keyword(s):

Dielectric Constant ◽

Dft Calculations ◽

Bond Length ◽

Dielectric Layer ◽

Room Temperature ◽

High Dielectric Constant ◽

Temperature Dependent ◽

High Dielectric

Through DFT calculations, a Be0.25Mg0.75O superlattice having long apical Be–O bond length is proposed to have a high bandgap (>7.3 eV) and high dielectric constant (∼18) at room temperature and above.

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Temperature-induced structural phase transitions in RERhSn (RE = Y, Gd-Tm, Lu)

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1515/zkri-2021-2008 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Simon Engelbert ◽

Rolf-Dieter Hoffmann ◽

Jutta Kösters ◽

Steffen Klenner ◽

Rainer Pöttgen

Keyword(s):

Rare Earth ◽

Phase Transitions ◽

Driving Force ◽

Room Temperature ◽

Structural Phase ◽

Structural Phase Transitions ◽

Line Broadening ◽

X Ray Diffraction ◽

Temperature Dependent ◽

X Ray

Abstract The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

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Direct measurement of the thermoelectric properties of electrochemically deposited Bi2Te3 thin films

Scientific Reports ◽

10.1038/s41598-020-74887-z ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Jose Recatala-Gomez ◽

Pawan Kumar ◽

Ady Suwardi ◽

Anas Abutaha ◽

Iris Nandhakumar ◽

...

Keyword(s):

Thin Films ◽

Thermoelectric Properties ◽

Bismuth Telluride ◽

Indium Tin Oxide ◽

Seed Layer ◽

Room Temperature ◽

Low Cost ◽

Temperature Dependent ◽

Temperature Heat ◽

Electrochemically Deposited

Abstract The best known thermoelectric material for near room temperature heat-to-electricity conversion is bismuth telluride. Amongst the possible fabrication techniques, electrodeposition has attracted attention due to its simplicity and low cost. However, the measurement of the thermoelectric properties of electrodeposited films is challenging because of the conducting seed layer underneath the film. Here, we develop a method to directly measure the thermoelectric properties of electrodeposited bismuth telluride thin films, grown on indium tin oxide. Using this technique, the temperature dependent thermoelectric properties (Seebeck coefficient and electrical conductivity) of electrodeposited thin films have been measured down to 100 K. A parallel resistor model is employed to discern the signal of the film from the signal of the seed layer and the data are carefully analysed and contextualized with literature. Our analysis demonstrates that the thermoelectric properties of electrodeposited films can be accurately evaluated without inflicting any damage to the films.

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A flexible microporous framework with temperature-dependent gate-opening behaviours for C2 gases

Chemical Communications ◽

10.1039/d1cc00014d ◽

2021 ◽

Vol 57 (31) ◽

pp. 3785-3788

Author(s):

Zhenyu Ji ◽

Yerong Fan ◽

Mingyan Wu ◽

Maochun Hong

Keyword(s):

Room Temperature ◽

Temperature Dependent ◽

Gate Opening ◽

Flexible Framework

A flexible framework has uncommon temperature-dependent gate-opening behaviors for C2 gases around room temperature.

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A 35-year-old mystery solved: a facile synthetic route and structural confirmation of tetrachlorobis(diethyl ether)tungsten(IV)

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229621002412 ◽

2021 ◽

Vol 77 (4) ◽

Author(s):

Thomas E. Shaw ◽

Alfred P. Sattelberger ◽

Titel Jurca

Keyword(s):

Crystal Structure ◽

Diethyl Ether ◽

Thermal Instability ◽

Room Temperature ◽

Surface Characteristics ◽

Hirshfeld Surface ◽

Asymmetric Unit ◽

Synthetic Route ◽

X Ray ◽

Elemental Analyses

The true identity of the diethyl ether adduct of tungsten(IV) chloride, WCl4(Et2O) x , has been in doubt since 1985. Initially postulated as the bis-adduct, WCl4(Et2O)2, questions arose when elemental analyses were more in line with a mono-ether adduct, viz. WCl4(Et2O). It was proposed that this was due to the thermal instability of the bis-adduct. Here, we report the room-temperature X-ray crystal structure and Hirshfeld surface characteristics of trans-tetrachloridobis(diethyl ether)tungsten(IV), trans-WCl4(Et2O)2 or trans-[WCl4(C4H10O)2]. The compound crystallizes, with half of the molecule in the asymmetric unit, in the centrosymmetric space group P21/n. The W—O distance is 2.070 (2) Å, while the W—Cl distances are 2.3586 (10) and 2.3554 (10) Å.

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