Materials Letters: X最新文献

In the present work, we have synthesized Ca_1.02Sr_1.98Al₂O₆ phosphors with different doping concentrations of Dy³⁺ (0.5 mol% to 4.0 mol%) by simple combustion method. The phase purity of the prepared phosphor has been confirmed by X-ray diffraction (XRD). Detailed investigations have been carried out to study the photoluminescence (PL) and thermoluminescence (TL) properties of the synthesized phosphors. Under 348 nm excitation, the PL emission spectrum shows two intense emission bands at blue and yellow color region due to the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transition of Dy³⁺ ions. In addition, the TL properties of gamma-irradiated Dy³⁺ doped Ca_1.02Sr_1.98Al₂O₆ phosphors were investigated. According to the obtained PL and TL results, the synthesized phosphors have good prospects for future investigations on white LED and TLD applications.

The effect of nitrogen (N₂) partial pressure on the structure and bandgap tunability of RF magnetron sputtered Cadmium Sulphide (CdS) thin films is investigated by varying N₂ partial pressure in Ar/N₂ mixture. In presence of N₂, films have a polycrystalline structure with (0 0 2) preferential orientation, which leads to defect-free, continuous, dense, and fibrous structures with increased roughness. The average optical transmittance increased to > 80 at 500–2500 nm for 30 % N₂ partial pressure, whereas the band gap decreases from 2.45 eV to 2.30 eV with increasing N₂ concentration. This work shows that the bandgap of sputtered CdS thin films can be tuned with the variation of N₂ concentration for customized applications.

Nickel-copper chromite (NiCuCr₂O₄) was synthesized by the co-precipitation method using sodium hydroxide as a precipitating agent. The composition of ammonium nitrate (AN):NiCuCr₂O₄ (mass ratio 98:2) was used for the comparative thermal analysis study. The results suggested that ammonium nitrate containing nickel-copper chromite (AN + NiCuCr₂O₄) can act as a potential energetic material to replace AN in energetic applications. The activation energy of AN + NiCuCr₂O₄ was decreased by 85.7 kJ mol⁻¹ compared to pure AN along with a reduction in the peak decomposition temperature. The lower activation energy and low pre-exponential factor can fasten AN + NiCuCr₂O₄’s decomposition at a lower temperature.

A novel ultrasonic vibration assisted laser beam oscillation welding (UV-LBOW) method was developed and applied on the butt-welding of Al-Mg alloy sheets. Due to the synergistic enhancement of the molten pool flow by ultrasound vibration and laser beam oscillation, the microstructure morphology of fusion zone (FZ) was comprised of equiaxed grains. Additionly, a uniform element distribution was generated from the boundary to the center of the FZ. An enhanced tensile strength of 347 MPa and a fraction elongation of 19.0 % were obtained due to the grain refinement and solid solution strengthening effects.

The focus of the present review is to provide a detailed discussion about the outstanding properties, namely physical, optical (majorly quantum confinement phenomenon), and electrical of cadmium selenide quantum dots (CdSe QDs). CdSe QDs have extensive utility in the biomedical domain owing to their unique properties. Thus, this review illustrates the wide range of applications of CdSe QDs in optical features, such as targeted drug delivery, drug resistance, drug analysis, photo-thermal therapy, antimicrobial activity, and tissue staining. Moreover, this review also highlights by discussing about the optical and optoelectronic application, which includes a good display, lasing, light emitting diode, and bioimaging that requires elevated photoluminescence spectra, quantum yield, and photostability.

A series of Ba₂Ca(PO₄)₄:Dy³⁺ phosphors were synthesized by the wet chemical method and the photoluminescence properties were systematically investigated. Under the 350 nm near ultraviolet excitation, Ba₂Ca(PO₄)₄:Dy³⁺ phosphor shows emission peak at 475 nm (blue) and 572 nm (yellow). At 0.5 mol% of Dy³⁺ ions, concentration quenching was shown. The present study implies that the Ba₂Ca(PO₄)₄:Dy³⁺ phosphors would be a suitable choice for solid-state lighting applications as a near ultraviolet convertible phosphor.

Aluminum oxide phosphors were synthesized by solution combustion method using urea and glycine as fuel. XRD results show that the sample synthesized with urea as a fuel is $\alpha -A{l}_2{O}_3$ and glycine as a fuel is $\gamma -A{l}_2{O}_3$ with rhombohedral (R-3c) and cubic (Fd-3m) structures, respectively. The PL spectra of unirradiated and Ni⁷⁺ ions irradiated $\alpha -A{l}_2{O}_3$ show a broad peak between 1.92 and 3.2 eV with maxima at 2.25 eV. This broad emission is assigned to the combination of F₂ and $F_2^{2+}$ centers. In addition, two sharp emissions observed at 1.83 eV (678 nm) and 1.78 eV (695) are due to R-lines of Mn⁴⁺ and Cr³⁺ respectively. The PL intensity is enhanced after Ni⁷⁺ ion irradiation in $\alpha -A{l}_2{O}_3$ and the highest intensity is observed for 1 × 10¹² Ni⁷⁺ cm⁻². PL intensity decreases beyond this fluence. Unirradiated $\gamma -A{l}_2{O}_3$ samples have greater PL intensity, which decreases with Ni⁷⁺ ion irradiation. PL emissions of R-lines of Mn⁴⁺ and Cr³⁺ are missing in $\gamma -A{l}_2{O}_3$ due to a lower crystal field in the gamma phase.

The chemical instability of CaS:Eu phosphors is a curial problem that hinders its practical application, especially under high temperature and humid environment. In this work, CaS:Eu capped by methacrylate-functionalized Si compound are successfully prepared under a mild condition, without seriously sacrificing the photoluminescence capability. The stability of the as-prepared samples is subsequently tested in stirred hot water (90 °C) for over a month, the outstanding hydrophobicity and chemical stability of the as-prepared samples sufficiently reserve the optical and chemical properties. Systematic characterizations are conducted to reveal the chemical features of the modified CaS:Eu phosphor.

A series of KCaPO₄:Eu³⁺ phosphors was effectively synthesized utilizing a wet chemical method. The photoluminescence excitation and emission properties of the phosphor were investigated. The KCaPO₄:Eu³⁺ phosphor was efficiently excited at 394 nm, and the PL (Photoluminescence) emission spectra were obtained at 591 and 614 nm. Concentration quenching occurred at a Eu³⁺ ion concentration of 0.5 mol%. The present work suggests that the KCaPO₄:Eu³⁺ phosphors may be a potential candidate as a near-UV (Ultraviolet) convertible material for solid state lighting applications.

Mn⁴⁺ is an impressive activator and sensitizer for luminescent material, which has been comprehensively investigated during the recent decades. In the present work, we give an account of the luminescence properties of Mn⁴⁺ activated KBa(PO₃)₅ glasses are successfully synthesized by using Melt quenching technique. SEM investigation confirms the proposed phosphite glass's morphological behaviour. A photoluminescence research showed that the proposed phosphor's emission peak was positioned in the far red emission area after being excited in the blue region. There are numerous indications that the peaks seen in the 650–750 nm region are helpful for growing plants. Therefore, the suggested glass sample is a promising contender for the use of cultivating far-red emitting plants.