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Particularities of trichloroethylene photocatalytic degradation over crystalline RbLaTa2O7 nanowire bundles grown by solid-state synthesis route
摘要： This is the first report on synthesis and photocatalytic activity for trichloroethylene (TCE) degradation under simulated solar light over RbLaTa2O7 layered perovskites with predominant nanowire or platelet morphologies. SEM images witnessed that the one step thermal treatment at 1200 °C lead to formation of RbLaTa2O7 nanowires with diameter of 80~320 nm and several microns in length associated in bundles and sharp-edged, merged platelets (minor phase). The two-step annealing at 950 °C and 1200 °C resulted in decrease of wires bundle population and increase in that of platelets merged in facetted particles. The RbLaTa2O7 nanowires are made of by well-aligned atomic rows with preferred orientation toward the c-axis, relatively free of defect. High density of hydroxyl groups on the sample calcined in mild conditions (RbLaTa_01) favors the photo mineralization of TCE. In contrast, the activity of RbLaTa_02 annealed in harsh conditions (950 and 1200 oC), poor in surface hydroxyl groups, remained modest. The weak surface basicity directed the reaction mainly to generation of intermediate chlorinated compounds. Pd and Au were supported on RbLaTa2O7 perovskites as an alternative strategy to boost the removal of chlorinated pollutants by combining photocatalytic (mineralization) and catalytic (hydrodechlorination, HDC) processes. The mineralization of TCE to Cl- was drastically hindered in presence of methanol due to quenching of ?OH radicals by alcohol. The results suggested that the density of RbLaTa2O7 surface hydroxyl groups is essential for photo mineralization of TCE whereas the surface carbonate is beneficial for the formation of intermediate chlorinated product.
关键词： solid state reaction,layered perovskites,trichloroethylene,simulated solar light,photocatalysis
更新于2025-09-23 15:21:21
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A facile route for synthesis of highly pure α-CaB4O7 compound
摘要： In this study, a facile route was developed for the synthesis of α-CaB4O7 compound. Ammonium tetraborate tetrahydrate (ATB) was used as the source of Boron. The compound was obtained using high-temperature solid-state reaction technique (840°C) and heat treatment process was introduced to enhance the phase purity and crystallinity. To control the formation of calcium tetraborate single phase, an excess amount of B2O3 (2wt%) was added to the starting powder mixture. Various analytical methods such as X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopies, Field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the prepared sample. Phase purity and crystallinity were evaluated by X-ray diffraction analytic method. Raman and FTIR spectroscopies were performed to confirm the atomic bond formation and its borate anionic group. FE-SEM was carried out for the morphological study of α-CaB4O7 compound and Energy dispersive X-ray (EDX) analysis was used to investigate the elemental composition of the prepared sample. XRD analysis confirmed that the prepared sample has alpha phase structure with monoclinic symmetry. The peaks correspond to unwanted phases (CaB2O4, Ca2B6O11) were not observed in the X-ray diffraction pattern of the prepared CaB4O7 compound. XPS was performed and its spectrum showed all expected characterization peaks for the first time, which is in agreement with FE-SEM and EDX results.
关键词： CaB4O7 compound,solid-state reaction,phase purity,highly crystalline
更新于2025-09-23 15:21:21
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Tunable bluea??greena??emitting Na4CaSi3O9:Ce3+,Li+,Tb3+ phosphor with energy transfer for near-UV white LEDs
摘要： Phosphor-converted white light emitting diodes (w-LEDs), with high luminous ef?ciency, low energy consumption, extended lifetime, and eco-friendly nature, have revolutionized various industries. Among them, an alkaline earth silicate-based phosphor host, Na4CaSi3O9, shows good crystal structure stability and ?exible properties for diverse application. Here, Ce3t/Lit and Tb3t/Lit co-doped Na4CaSi3O9 phosphors are fabricated by the standard solid-state reaction approach. The Ce3t/Lit-activated phosphors show strong absorption within 200e400 nm and exhibit a blue emission centered at 423 nm. The quenching concentration of Ce3t appears at x ? 0.05 and can be attributed to the dipoleequadrupole interaction. When Tb3t ions are co-doped, the Na4CaSi3O9:Ce3t/Lit phosphor emission can be adjusted from blue to green under the irradiation of 365 nm through the dipoleedipole interaction induced energy transfer from Ce3t to Tb3t ions with a maximum value of 28.32%. This study highlights the Na4CaSi3O9:Ce3t/Lit,Tb3t/Lit phosphors as a new and ef?cient material for w-LED applications.
关键词： Phosphor,Solid-state reaction,Luminescence,LED,Energy transfer
更新于2025-09-23 15:21:01
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A study on structural, spectral, and magnetic properties of Pr–Bi co-doped M-type barium–strontium hexaferrites via the solid-state reaction method
摘要： Pr–Bi co-doped M-type Ba–Sr hexaferrites with nominal compositions Ba0.35Sr0.65?xPrxFe12.0?xBixO19 (0.00 ≤ x ≤ 0.40) were synthesized for the first time by the solid-state reaction method. These hexaferrites were characterized by X-ray diffractometer (XRD), Fourier transformer infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM) and thermogravimetric analyzer (TGA). XRD patterns showed that the single M-type hexaferrite phase was obtained only if Pr–Bi content (x) ≤ 0.24. FT-IR frequency bands in the range (608–610) cm?1 and (445–447) cm?1 correspond to the formation of tetrahedral and octahedral clusters of metal oxides in the hexaferrites, respectively. FE-SEM micrographs indicated that the grains were of platelet-like shapes. The saturation magnetization (Ms), remanent magnetization (Mr), magnetic anisotropy field (Ha), first anisotropy constant (K1) and coercivity (Hc) first increased with Pr–Bi content (x) from 0.00 to 0.08, and then decreased when Pr–Bi content (x) ≥ 0.08. The Curie temperature (Tc) decreased with increasing Pr–Bi content (x) from 0.00 to 0.40.
关键词： Pr–Bi co-doped,structural properties,solid-state reaction method,spectral properties,magnetic properties,M-type barium–strontium hexaferrites
更新于2025-09-23 15:21:01
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(Ba,Sr)LaZnTaO6:Mn4+ far red emission phosphors for plant growth LEDs: structure and photoluminescence properties
摘要： It is necessary to develop novel high-efficient red or far-red-emitting in order to facilitate the phosphor-converted light-emitting diodes (pc-LEDs) for plant growth. This work reports a series of novel far-red emitting (Ba,Sr)LaZnTaO6:xMn4+ phosphors with double perovskite structure synthesized by traditional high-temperature solid-state reaction (SSR) process. The crystal structure and morphology of (Ba,Sr)LaZnTaO6 are investigated by high-resolution TEM, SEM, and XRD Rietveld refinement. The photoluminescece properties are systematically explored and analyzed by diffuse reflection (DR) spectra, photoluminescence emission (PL) and excitation (PLE) spectra, decay curves and temperature-dependent spectra. Mn4+ ions occupy Ta5+ sites located at [TaO6] octahedral emitting red light with peak at 698 nm in BaLaZnTaO6:Mn4+ and 695 nm in SrLaZnTaO6:Mn4+ under n-UV and blue light excitation. The critical quenching concentration of Mn4+ was determined to be 0.008. The concentration quenching mechanism could be a dipole-dipole interaction between Mn4+ ions. In addtion, the PL intensity of (Ba,Sr)LaZnTaO6:xMn4+ phosphors decrease with increasing temperature. The SrLaZnTaO6:xMn4+ sample has better thermal stability than BaLaZnTaO6:xMn4+. Interestingly, (Ba,Sr)LaZnTaO6:0.008Mn4+ exhibits outstanding internal quantum efficiency (IQE ≥ 80 %). Fianally, the fabricated of LEDs are combined with SrLaZnTaO6:0.008Mn4+ phosphors combined with 460 nm InGaN chips, which emit blue and red light. Based on above properties, the rare-earth-free (Ba,Sr)LaZnTaO6:xMn4+ phosphors have great potentials to be serviced as far-red emitting phosphors in high-power plant growth LEDS.
关键词： double perovskite structure,phosphor-converted light-emitting diodes,internal quantum efficiency,far-red emitting,plant growth,Mn4+,thermal stability,photoluminescence,solid-state reaction
更新于2025-09-23 15:19:57
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Mn <sup>4+</sup> -activated BaLaMgSbO <sub/>6</sub> double-perovskite phosphor: a novel high-efficiency far-red-emitting luminescent material for indoor plant growth lighting
摘要： In the present work, novel high-efficiency Mn4+-activated BaLaMgSbO6 (BLMS) far-red-emitting phosphors used for plant growth LEDs were successfully synthesized via a solid-state reaction method. X-ray diffraction (XRD), photoluminescence (PL), temperature-dependent PL, CIE color coordinates, and lifetimes as well as internal quantum efficiency (IQE) were used to characterize the phosphor samples. The excitation spectrum of the as-obtained BLMS:Mn4+ phosphors presented two wide bands covering 250–550 nm and the emission spectrum exhibited a far-red emission band in the range of 650–800 nm peaked at 700 nm. Concentration-dependent PL properties of BLMS:Mn4+ phosphors were studied. The optimal doping concentration of Mn4+ ions was 0.6 mol%, and the concentration quenching mechanism was determined to be the nonradiative energy transfer among the nearest-neighbor Mn4+ activators. Impressively, the BLMS:0.6%Mn4+ sample showed an outstanding IQE of 83%. In addition, the luminescence thermal quenching characteristics were also analyzed. Furthermore, the PL spectrum of BLMS:0.6%Mn4+ sample was compared with the absorption spectrum of phytochrome PFR. Finally, after combining BLMS:0.6%Mn4+ phosphors with a 365 nm near-UV LED chip, a far-red light-emitting diode (LED) device was successfully achieved to demonstrate its possible applications in plant growth LEDs.
关键词： far-red-emitting,solid-state reaction,Mn4+-activated,internal quantum efficiency,plant growth LEDs,phosphor,BaLaMgSbO6
更新于2025-09-19 17:15:36
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Effect of yttrium insertion on the structural, optical, vibrational and dielectric properties of 0.3Bi1?yYyFeO3–0.7Ba0.8Sr0.2TiO3 ceramics
摘要： Perovskite ceramics [Ba0.8Sr0.2]1-x[Bi1-yYy]xTi1-xFexO3 with x = 0.3 and 0.05 \ y \ 0.15 are synthesized by solid-state solution in order to study the effect of yttrium insertion on the physical properties of this material. The XRD patterns showed the formation of single tetragonal phase without any impurities. Using UV–Vis spectroscopy, the absorbance and re?ectance are highlighted. In fact, we note a blueshift on wavelength and the energy band gap is increased with a high doping content. Besides, Raman spectra display a drop in mode intensities, which is followed by the rise of yttrium that can lead to a ?uctuation in the atomic structure. Furthermore, the permittivity and loss dielectric are studied by impedance spectroscopy, revealing that both decrease with rising frequency indicating, as a result, a dielectric dispersion. Finally, the study of permittivity dielectric as a function of temperature exhibits the presence of G-type antiferromagnetic transition.
关键词： Structural analysis,Ba0.8Sr0.2TiO3,Dielectric response,Optical properties,Solid-state reaction,BiFeO3,Raman spectra
更新于2025-09-19 17:15:36
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Facile synthesis of ZnO microrod photodetectors by solid-state reaction
摘要： In this study, ZnO microrods were directly synthesized via a single-step solid-state reaction using ZnO powders mixed with graphite without a catalyst under an air atmosphere, instead of using vacuum systems and flowing gases. The structure, growth mechanism, and electrical and optical properties of the microrods were investigated under varying growth conditions. The high-resolution transmission electron microscopy images confirmed the formation of single-crystal ZnO microrods. The photoluminescence spectra of the microrods showed green emission, suggesting the formation of non-stoichiometric ZnO microrods due to the formation of oxygen vacancies during sintering. The length and width of the ZnO microrods could be modulated by controlling the graphite content, sintering temperature, and residual time. A simple photodetector consisting of a single-crystal ZnO microrod on a SiO2-coated Si substrate was fabricated. The photodetector exhibited a linear current–voltage curve in visible light. The slope of the curve increased under ultraviolet (UV) irradiation, maintaining a linear shape of the curve. The curve reversibly returned to the initial shape in the absence of UV illumination. The UV on-off current ratio increased because of the decrease in the off-current by compensating for the oxygen vacancies through annealing in an oxygen atmosphere. Thus, in this study, we proposed a simple and efficient approach to fabricate single-crystal ZnO microrods for application in low-cost photodetectors.
关键词： oxygen vacancies,solid-state reaction,single-crystal,ZnO microrods,photodetector
更新于2025-09-19 17:13:59
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Kinetics of Cr <sup>3+</sup> to Cr <sup>4+</sup> ion valence transformations and intra-lattice cation exchange of Cr <sup>4+</sup> in Cr,Ca:YAG ceramics used as laser gain and passive Q-switching media
摘要： This paper focuses on the kinetics of Cr4+ formation in Cr,Ca:YAG ceramics prepared by solid-state reaction sintering. The kinetics of Cr4+ formation was studied by annealing of Cr,Ca:YAG ceramics in ambient air under different temperatures at different times, resulting in the transformation of Cr3+ to Cr4+. The activation energy (Ea) of Cr3+ oxidation determined by the Jander model was 2.7 ± 0.2 eV, which is in good correlation with the activation energy of innergrain oxygen diffusion in the YAG lattice. It is concluded that Cr3+ to Cr4+ transformation in YAG ceramics is limited by oxygen diffusion through the grain body. It was established that in Cr,Ca:YAG ceramics, the intralattice cation exchange, in which the Cr4+ ions exchange positions with the Al3+ ions, switching from “A” to “D” sites, is faster than Cr3+ to Cr4+ oxidation. In the temperature range of 900–1300 ○C, the reaction enthalpy of Al3+/Cr4+ ion exchange between octahedral “A” and tetrahedral “D” lattice sites is close to zero, and this exchange ratio is thermodynamically driven by entropy.
关键词： intralattice cation exchange,Cr4+:YAG ceramics,solid-state reaction sintering,oxygen diffusion,Cr3+ oxidation
更新于2025-09-16 10:30:52
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Ideal Laser Cooling Efficiency Utilizing Anti-Stokes Luminescence in Yb-Doped Yttrium Aluminum Garnet Powder Crystals; Yb添加イットリウムアルミニウムガーネット結晶粉末におけるアンチストークス発光を利用した理想レーザー冷却効率;
摘要： Laser cooling in rare-earth doped material using anti-Stokes photoluminescence (PL) caused by phonon annihilation realizes novel cooling devices without generating heat and vibration. Yb-doped yttrium aluminum garnet powder crystals, (Y:Yb)AG with the Yb concentration from 2 to 13 mol%, were fabricated by a solid state reaction method. PL of (Y:Yb)AG excited at 659 nm shows the maximum intensity at the Yb concentration of 6 mol% because of concentration quenching of the PL. When we resonantly excite at 1030 nm corresponding to the energy distance between the E5 and E3 levels of the f-f transition of Yb3+, obvious anti-Stoke PL signal has been observed at 968 nm. This result indicates that phonons are absorbed, and, then, an up-converted photon with the energy between the E5 and E1 levels is emitted. The relative cooling efficiency, defined by a product of the ideal cooling efficiency and the integrated PL intensity, becomes maximum at the 1030-nm excitation. The ideal cooling efficiency was estimated to be 1.9% at the Yb concentration of 6 mol% and the 1030-nm excitation at room temperature.
关键词： Self-absorption,Solid state reaction,Phonon absorption,(Y:Yb)AG,Rare-earth,Laser cooling in solids
更新于2025-09-11 14:15:04