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Time-resolved structure analysis of piezoelectric crystals by X-ray diffraction under alternating electric field
摘要： Rare-earth substitution effects on atomic motions in resonantly vibrating piezoelectric oscillators of langasite-type crystals, namely, La3Ga5SiO14 (LGS) and Nd3Ga5SiO14 (NGS), are revealed by time-resolved X-ray crystal structure analysis under alternating electric fields. Deformations of Ga–O–Ga and Ga–O–Ga/Si bond angles accompanying deformations of RE–O (RE: La or Nd) bond lengths found in LGS are suppressed in NGS. Alternatively, rigid GaO6 octahedra are deformed in NGS. The decreases in RE–O bond lengths and Ga–O–Ga and Ga–O–Ga/Si bond angles caused by the substitution of La by Nd would make the bond lengths and angles more difficult to deform under electric fields; hence, the piezoelectric constants of NGS are smaller than those of LGS.
关键词： rare-earth substitution,piezoelectric crystals,alternating electric field,X-ray diffraction,time-resolved structure analysis
更新于2025-09-09 09:28:46
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Application of Biophotonics with Near Infrared Excitation for Theranostics; 近赤外励起バイオフォトニクスのセラノスティクスへの展開;
摘要： Near infrared wavelength region is known to have the most transparency of live body for electromagnetic wave with wavelength around the visible wavelength. Namely, the near infrared with a wavelength longer than 1000 nm (OTN-NIR) shows more transparency than that with shorter wavelength. The observation depth can be several centimeters with the OTN-NIR fluorescence, while that is limited to be only several millimeters with visible fluorescence. As OTN-NIR fluorescent agents, dyes, quantum dots, carbon nanotubes and rare-earth doped ceramic nanoparticles (RED-CNP) are known. A special feature of the RED-CNP is to show infrared-to-visible upconversion to emit visible light with a near infrared excitation, simultaneously with the OTN-NIR fluorescence. As a theranostic approach, nanomaterials for achieving photodynamic therapy with the near infrared excitation are introduced. Another special feature of the RED-CNP is the potential use for fluorescence nanothermometry. A scheme for ratiometric fluorescence nanothermometry with the OTN-NIR fluorescence is described. By using a RED-CNP with holomium and erbium co-doping, ratiometric fluorescence nanothermometry was successfully demonstrated. As shown with the case of photodynamic therapy with near infrared excitation, by applying an upconversion excitation scheme, visible light emission for photochemical reaction is possible with a near infrared excitation with high transparency in a live body. By constructing these multiple functions on the RED-CNP, various theranostic approach can be achieved. The size and bio distribution controls are important issues for applications of the RED-CNP for medical applications.
关键词： thermometry,near infrared,nanoparticle,rare-earth,PDT
更新于2025-09-09 09:28:46
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Tuning visible emission from red to yellow of PbWO4:Yb3+/Ho3+ nanophosphor by modulating activator ion concentration
摘要： Lanthanide doped upconverting nanophosphors possesses a great appulse in many emerging applications due to their stupendous luminescence property, photostability, effective quantum efficiency, etc. In this article Yb3+ and Ho3+ doped lead tungstate synthesized by hydrothermal method has been reported. The synthesized materials were characterized by XRD, FTIR, HRTEM and photoluminescence study was carried out with the help of spectroflurophotometer. The synthesized nanophosphor is an exposition of a strong red emission which was tuned to yellow emission by increasing the concentration of Ho3+ based on green emission at 542 nm due to 5S2/5F4→5I8 transition of Ho3+ and red emission at 657 nm due to 5F5→5I8 transition of Ho3+ upon excitation at 980nm. The study of dependency of emission intensity with pump power as lnP vs lnI curve corroborate that the upconversion mechanism involves two photon process. The radiative lifetimes measured for the emission were 23.31 μs for green emission (5S2/5F4→5I8) and 50.96 μs for red emission (5F5→5I8). The club-shaped nanophosphor which we have synthesized can be bestowed in different sectors as it has a tuneable red to yellow emission characteristics and hence, it could be exercised in many applications.
关键词： Lead tungstate,Hydrothermal,Rare-earth,Upconversion,Nanophosphor
更新于2025-09-09 09:28:46
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Tuning the optical properties of ZnO:Cd by doping La and Y
摘要： Zinc oxide doped with Cadmium and rare earth elements synthesized by solgel auto combustion route is reported in this work. The studies have been carried out to analyze the structural, morphological and optical properties of Cd doped ZnO and rare earth doped ZnCdO. The XRD analysis reveals that the addition of rare earth impurity decreases the particle size of ZnCdO. La doped ZnCdO has the least particle size among the samples of ZnCdO and rare earth doped ZnCdO. The morphological changes due to the addition of rare earth impurities have been found. Samples of La doped ZnCdO shows a pillar like morphology. The hexagonal structures are prominently seen in the SEM micrographs of the samples of ZnCdO. The UV-Visible spectral analyses show that the bandgap reduces when ZnCdO is doped with the rare earth impurities. The photoluminescence spectra show the broad spectrum in visible region exhibited by ZnO and a scanty UV emission. The UV emission of rare earth doped samples decreases due to the destruction in the crystal structure. The rare earth doped ZnCdO shows a small peak in green emission that decreases when rare earth impurities are doped. There is a uniform spectral response other than a small Gaussian like green peak. The overall analyses show that the samples can be used in optoelectronic applications to work in the visible region.
关键词： rare earth elements,structural properties,optical properties,UV-Visible spectral analyses,Cadmium,SEM micrographs,photoluminescence spectra,XRD analysis,Zinc oxide,solgel auto combustion,morphological properties
更新于2025-09-09 09:28:46
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Structural, morphological, optical and dielectric properties of M <sup>3+</sup> /PVA/PEG SPE Films (M = La, Y, Fe or Ir)
摘要： Low band gap polymer complexes are promising due to its flexibility, and exhibiting electronic and optical properties of inorganic semiconductors. The effect of PEG on the physical properties of PVA was evaluated. Then, blend (PVA: PEG = 50:50) doped with rare earth (La or Y) and transition metal (Fe or Ir) chlorides to obtain solid polymer electrolyte films. XRD shows that adding PEG to PVA results in a new peak, 2θ = 23o with increased intensity as PEG ratio increases. However, doping with La3+, Fe3+ or Ir3+ eliminate this peak and decrease the crystallinity. SEM exhibits significant changes in the morphology of films. FTIR confirms miscibility between PVA & PEG and the complexation of the salts. The optical band gap (Eg) of PVA ~ 5.37 eV, decreased slightly by blending with PEG. While it decreased significantly to 2.64 eV and 2.78 eV after doping with Fe3+ or Ir3+. There are a consistency between Eg values obtained by Tauc's model and that obtained from the optical dielectric loss. The dielectric constant and loss, in temperature range 303–405 K & frequency range 1.0 kHz ‐ 5.0 MHz, indicate one or two relaxation peak(s) depending on the film composition. Accordingly, conduction mechanism varied between correlated barrier hopping and large polaron tunneling. The DC conductivity was strongly depend on the dielectric loss. The transition metal salts appear to be more effective than the rare earth ones in increasing σac of films to higher values that candidates them in semiconductors industry.
关键词： conduction mechanism,low band gap polymers,activation energy,PVA/PEG blend,rare earth metal complexation,solid polymer electrolyte
更新于2025-09-09 09:28:46
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Aliovalent Ho3+ ion doped BaZrO3 thin films; Structural, optical and photoluminescence properties
摘要： Ho doped BaZrO3 thin film phosphors with varying Ho content (1, 2, 3 and 4 at. %) were prepared via pulsed laser deposition technique. To understand the effect of doping on structural, morphological, optical and emission properties of thin films, X-ray Diffractrometer (XRD), Scanning Electron Microscopy (SEM), Spectroscopic Ellipsometry (SE) and Photoluminescence (PL) Spectroscopy have been used, respectively. Polycrystalline nature with single phase cubic crystalline structure of the films has been obtained. The optical band gap energy, as estimated by SE, has been found to increase with increase in the Ho content. The PL spectra of the synthesized phosphor exhibit green and yellow-orange as prominent emission bands in response to 328 nm as excitation wavelength.
关键词： optical properties,thin films,rare earth,perovskite
更新于2025-09-09 09:28:46
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Electroluminescence of intrashell transitions in Eu doped single ZnO nanowires
摘要： Tunable nanoscale light emitters are essential to accomplish future multifunctional optoelectronic nano-devices. Here, we present an approach for achieving red electroluminescence from single ZnO nanowires implanted with Europium ions. The electroluminescence is emitted mainly from the end facets of ZnO nanowires at room temperature under the application of an AC voltage. The corresponding electroluminescence spectrum is attributed to the radiative intrashell transitions of the Eu ions, while contributions from near band edge or deep level emission of the ZnO remain absent. The total intensity of the electroluminescence is linearly proportional to the length of the nanowires, whereas there is no clear correlation with other morphology factors of the nanowire based device such as the diameter. Furthermore, the underlying excitation mechanism of the electroluminescence is proposed as direct-impact excitation of Eu ions by hot electrons in the ZnO nanowires.
关键词： electroluminescence,Zinc oxide (ZnO),Europium (Eu),nanowires,rare earth elements,ion beam doping
更新于2025-09-09 09:28:46
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Solar Blind UV Light Induced Photo‐Voltage from Transparent Y <sub/>2</sub> O <sub/>3</sub> : Eu‐PMMA Nanocomposite Film
摘要： Transparent inorganic-organic nanocomposite film (Y2O3: Eu-PMMA)W is fabricated for solar blind UV light photo-voltage response at room temperature. In suggested design, Y2O3: Eu nanoparticales with efficient visible luminescence excited under solar blind UV light is incorporated into an Y2O3: Eu-PMMA nanocomposite film coated onto a glass substrate, which converts solar blind UV light to visible light that is absorbed by the Si-detector. Photo-voltage response from the thin film Si-APD detector attached with the inorganic-organic nanocomposite film demonstrates a prospective application for solar blind UV light detection.
关键词： luminescence,UV detector,rare-earth-doped materials,solar blind UV light
更新于2025-09-04 15:30:14
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Recovering the “new twin”: Analysis of secondary neodymium sources and recycling potentials in Europe
摘要： Sustainable management strategies for securing long–term supply of rare earth elements is priority for Europe due to a complex and interlinked production chain and its dependence on Chinese export. Among rare earth elements, neodymium captured most attention due to its essential role in a wide spectrum of applications including green–energy technologies such as wind turbines and electric vehicles. Being complementary to primary production, end–of–life recycling would diversify neodymium supply, relieve the Chinese dominance on primary production and contrast the balance problem. However, neodymium recycling at end–of–life is not yet in place. In this work, we developed a dynamic material ?ow model to investigate neodymium stocks and ?ows in the EU–28 to 2016. The analysis enabled a detailed investigation of secondary sources of neodymium, which set essential boundary conditions for material recovery and recycling. We found that roughly up to 50% of the annual neodymium demand in the EU–28 could be met by domestic secondary supply, if latent recycling potentials were turned into actual capacity. Signi?cant energy savings and GHG emissions cut could be also attained. However, product design, end–of–life collection, and scrap price issues are primary obstacles to neodymium recovery. Thus, unless going beyong those limits, establishing and maintaining a sustainable recycling chain for neodymium in the EU–28 will remain problematic.
关键词： Rare earth elements,Voice coil motors,Permanent magnets,Balance problem,Electric vehicles,Wind turbines
更新于2025-09-04 15:30:14
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High Pressure effect on fluorescence lifetime <i>τ</i> for magnetic dipole <sup>5</sup> D <sub/>0</sub> → <sup>5</sup> F <sub/>1</sub> transitions in YAG:Eu <sup>3+</sup>
摘要： The fluorescence lifetime for magnetic dipole 5D0→7F1 transition in yttrium aluminum garnet doped with Eu3+ (YAG:Eu3+) crystal was studied under the pressure of up to 10.4 GPa at room temperature. The fluorescence lifetime τ (5D0→7F1 transition) slowly decreased with pressure. The pressure effect on τ (5D0→7F1 transition) was explained with a model which considered pressure effect on line position: inter-ionic distance, ion volume, molecular volume, ion polarizability, molecular polarizability, sample refractive index, and surrounding hydrostatic medium refractive index. The fluorescence lifetime τ calculated by the presented model was in close correspondence with the experimental values.
关键词： rare earth,fluorescence lifetime,YAG:Eu3+,optical properties,glass ceramics,High pressure
更新于2025-09-04 15:30:14