High-temperature Solid-phase Method Research Articles

High Quantum Efficiency Rare-Earth-Doped Gd2O2S:Tb, F Scintillators for Cold Neutron Imaging.

High-resolution neutron radiography provides novel and stirring opportunities to investigate the structures of light elements encased by heavy elements. For this study, a series of Gd2O2S:Tb, F particles were prepared using a high-temperature solid phase method and then used as a scintillation screen. Upon reaching 293 nm excitation, a bright green emission originated from the Tb3+ luminescence center. The level of F doping affected the fluorescence intensity. When the F doping level was 8 mol%, the fluorescence intensity was at its highest. The absolute quantum yield of the synthesized particles reached as high as 77.21%. Gd2O2S:Tb, F particles were applied to the scintillation screen, showing a resolution on the neutron radiograph as high as 12 μm. These results suggest that the highly efficient Gd2O2S:Tb, F particles are promising scintillators for the purposes of cold neutron radiography.

Ca2YNbO6: Dy3+, Sm3+/Eu3+ warm white phosphors with tunable light color and FIR optical temperature measurement characteristics

The warm white phosphor samples Ca2YNbO6 (CYN): x mol Dy3+, y mol Sm3+/z mol Eu3+ were synthesized by the high-temperature solid-phase method. They have low CCT values and high thermal stability and still have more than 80% luminescence intensity at room temperature of 425 K, indicating that they can be used for WLED. The samples' emission (PLE) and excitation (PL) spectra were measured, and the reasons for the concentration quenching of CYN: x mol Dy3+, y mol Sm3+/z mol Eu3+ were analyzed. Meanwhile, it was found that the CYN: 0.05 mol Dy3+, 0.2 mol Eu3+ samples showed different trends in the two emission peaks of I575 and I612 under temperature variations. On this basis, an FIR temperature measurement model was developed with a maximum value of 3.14% k−1 for Sr, indicating that the sample has good optical temperature measurement characteristics.

Interaction of superionic conductor and heterostructure LiVOPO4-Li2.72Ti2(PO4)3 cathode materials for lithium-ion batteries

The heterostructure LiVOPO4-Li2.72Ti2(PO4)3 (LVOP-LTP) was synthesized using a hydrothermal process combined with a high-temperature solid-phase method. The electron microscopic analysis demonstrates that the sample has a heterojunction. The electrochemical performance tests reveal that the heterostructure LVOP-LTP has initial discharge-specific capacity of 88.4 mAh/g at 100 mA g−1, which is superior to the single-phase LiVOPO4 (LVOP, 25.1 mAh/g) and Li2.72Ti2(PO4)3 (LTP, 37.1 mAh/g). The improved electrochemical performance of heterostructure LVOP-LTP can be ascribed to the introduction of lithium superionic conductor (LISICON) and the formation of a heterojunction, which increases the lithium-ion pervasion channels and accelerates the lithium-ion transmission speed.

Al, Zr dual-doped cobalt-free nickel-rich cathode materials for lithium-ion batteries

Nickel-rich and cobalt-free cathode materials have obvious advantages in the aspects of energy density and economic efficiency. However, these materials are restricted from being used in commercial lithium-ion batteries due to the problems of poor structural stability and rate capability. In this study, the aluminum and zirconium dual-doped Co-free Ni-rich LiNi0.96Mn0.04O2 cathode material (NMAZ) is prepared by a facile high-temperature solid-phase method. The obtained NMAZ shows low cation disordering degree owing to the stability of transition metal slabs induced by strong Al–O and Zr–O bonds. Besides, the kinetics of lithium-ion diffusion is significantly improved by larger c-axis and the fast lithium-ion conducting Li2ZrO3 layer on the interface. As a result, NMAZ shows an improved capacity retention of 70.3% at 1C after 100 cycles under an elevated temperature (45 ​°C), compared with 50.5% of pure LiNi0.96Mn0.04O2. In addition, it exhibits splendid rate performance even at higher C-rate and better thermal stability compared to bare LiNi0.96Mn0.04O2. Hence, the Al, Zr dual-doped modification is beneficial to improving the structural stability and electrochemical performance of the Ni-rich and Co-free layered oxide cathodes for Li-ion batteries.

Dual-mode up/down-conversion optical thermometry of Pr<sup>3+</sup>-regulated Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup> phosphors

Photothermal sensing is crucial in developing smart wearable devices. However, designing and synthesizing luminescent materials with suitable multi-wavelength emission and constructing multiple sets of probes in a single material system is a huge challenge for constructing sensitive temperature sensors with a wide temperature range. In this paper, Pr<sup>3+</sup>, Er<sup>3+</sup> single-doped and double-doped Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub> phosphors are successfully prepared by high temperature solid phase method, and their structures, morphologies, excitation wavelengths and temperature-dependent fluorescence properties are characterized by XRD, SEM, fluorescence spectrometer and self-made heating device. Firstly, the photoluminescences of the synthesized series of samples are investigated. The results show that comparing with the single-doped Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>: Er<sup>3+</sup> sample, the up/down-conversion spectra of Pr<sup>3+</sup>, Er<sup>3+</sup> co-doped phosphors under 808 nm/380 nm excitation show that the green fluorescence emission of Er<sup>3+</sup> is enhanced. In addition, under 980 nm excitation, Pr<sup>3+</sup> can effectively regulate the fluorescence energy level population pathway, so that the electrons are more effectively arranged in the <sup>2</sup>H<sub>11/2</sub> and <sup>4</sup>S<sub>3/2</sub> energy levels in the excitation process. The red emission is weakened and the green emission is enhanced, which improves the signal resolution of the fluorescent material and has a significant influence on the optical temperature measurement. Secondly, the up-conversion fluorescence property of Er<sup>3+</sup> under 808 nm/980 nm laser excitation in Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup> and Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Pr<sup>3+</sup>,Er<sup>3+</sup> phosphors are investigated. The results show that the red and green fluorescence emissions of Er<sup>3+</sup> are two-photon processes. Finally, the up/down-conversion dual-mode temperature sensing properties of Er<sup>3+</sup> in Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup> and Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Pr<sup>3+</sup>, Er<sup>3+</sup> phosphors are investigated. It is found that both materials have good optical temperature measurement performances. The Pr<sup>3+</sup> doping optimizes the dual-mode optical temperature measurement performances of Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup> phosphors derived from the thermal coupling energy level of Er<sup>3+</sup> ions. In addition, the up/down-conversion fluorescence mechanism of Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup> and Li<sub>0.9</sub>K<sub>0.1</sub>NbO<sub>3</sub>:Er<sup>3+</sup>, Pr<sup>3+</sup> phosphors are proposed, and the enhanced green fluorescence by Pr<sup>3+</sup> co-doping is attributed to the energy transfer from Pr<sup>3+</sup> ions to Er<sup>3+</sup> ions, leading to the increase of green fluorescence level population and the decrease of red fluorescence level population of the Er<sup>3+</sup> ions. This new dual-mode optical temperature measurement material provides a material basis and optical temperature measurement technology for exploring other temperature measurement materials.

Synthesis and characterization of Zn1-xMnxO yellow pigment with high near-infrared reflectance

A series of Zn1-xMnxO (0.001 ≤ x ≤ 0.009) inorganic yellow pigments were prepared by a high-temperature solid-phase method using ZnO and MnO as raw materials. Powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric differential scanning calorimetry (TG-DSC) and so on were applied to test and analyze the designed pigments. The Zn1-xMnxO pigments do not contain rare earth elements. The raw materials required for the production of the pigment are readily available and the cost of raw materials is low. The pigment has a high near-infrared (NIR) solar reflectance of 71.87%–84.02%. The pigment can improve the NIR reflectance of the glaze. The box simulation experiment revealed that the Zn0.995Mn0.005O pigment has better thermal shielding performance than the commercial iron yellow pigment. Additionally, the pigment also has good chemical stability. Therefore, Zn1-xMnxO pigments have potential as cold pigments and can be applied to architectural coatings to achieve energy saving effects.

Luminescence properties and spectral modulation of the ultra-broadband, highly efficient near-infrared luminescent material CaGa4O7:Cr3+, Cr4+, Yb3+

Recently, near-infrared phosphors have received a lot of attention due to their wide application in the field of detection and analysis, and it is urgent to develop efficient broadband NIR phosphors. In this paper, a conventional high-temperature solid-phase method was used to prepare a novel near-infrared phosphor CaGa4O7:Cr3+, Cr4+, which provides two emission bands ranging from 600 to 1000 nm and 1100–1600 nm. Although there are only four and five coordination sites in the CaGa4O7 (CGO) lattice, the doping of the Cr3+ ions in the CGO causes the Ga–O tetrahedral distortion into an octahedron, providing a favorable environment for the emission of the Cr3+ ions. Under blue light excitation, Cr3+ emits luminescence in the NIR I region from 600 to 1000 nm with a half-height width of up to 148 nm. With increasing Cr ion concentration, more and more Cr4+ preferentially occupy the four coordinated Ga3+ sites, and the intensity of the ultra-broad emission band in the NIR II region (1100 nm–1600 nm) increases with a full width at half maximum (FWHM) of 262 nm. To further optimize the emission spectrum, Yb3+ was codoped into CGO: Cr3+, Cr4+, the energy transfers from Cr3+ to Yb3+ in CGO was found, thus filling the gap between 1000 and 1100 nm in the CGO emission spectrum and obtaining a more complete ultra-wide spectrum. Moreover, the luminescence mechanism, energy transfer efficiency, and quantum yield are also studied in detail, and the ability of CaGa4O7:Cr3+, Cr4+, and Yb3+ luminescent materials to achieve ultra-broadband efficient near-infrared emission was demonstrated.

Crystal growth and scintillation characterizations of mixed halide scintillators K2LaBr5-xIx: Ce (x = 0, 1, 2)

The purpose of this research is to investigate the luminescence and scintillation properties of mixed halide scintillators K2LaBr5-xIx. The crystals of K2LaBr5-xIx:2% Ce (x = 0, 1, 2) have been synthesized by high-temperature solid-phase method and grown by vertical Bridgman method. The crystals are measured by X-ray induced luminescence spectra, optical transmittance photoluminescence spectrum, photoluminescence decay time, and pulse height spectrum. Under the UV and X-ray excitation, all of the crystal samples have typical Ce3+ double peaks corresponding to the energy level shifts of 5d1→2F5/2 and 5d1→2F7/2, with emission centers ranging from 350 to 400 nm. The photoluminescence decay time of the three crystals of K2LaBr5-xIx: Ce is about 20 ns. Under 662 keV γ-rays excitation from a 137Cs source, the energy resolution is 8.2%, 15% and 10% (FWHM), respectively.

Mn2+ doped BaAl11O16N phosphors with narrow band green emission and superior thermal stability for backlighting display applications

Here, BaAl11O16N: Mn2+ green phosphor was synthesized by a two-step high-temperature solid-phase method, and its phase structure, morphology and photoluminescence properties were studied in detail. The phosphor has a wide excitation range of 240–500 nm, and the most effective excitation bands are in the blue spectral regions, indicating that BaAl11O16N: Mn2+ green phosphor can be effectively excited by the commercial blue LED chip. Under the excitation of ultraviolet and blue light, the BaAl11O16N: Mn2+ phosphor shows bright green light emission, with a peak of 514 nm and a half peak width of about 31 nm. The emission properties with temperature change show that the BaAl11O16N: Mn2+ phosphor has good thermal stability and excellent color stability. The white light-emitting diode (a blue InGaN chip combined with BaAl11O16N: 0.25Mn2+ phosphor and a commercial K2SiF6: Mn4+ phosphor) exhibits a NTSC value of 119.3%. Therefore, it can be concluded that the BaAl11O16N: Mn2+ phosphor the ideal choice for wide color gamut backlight as a potential efficient phosphor with green narrow-band emission.

Ionic selective occupation, lattice modulation and photoluminescence properties of garnet typed orange-yellow phosphors for white-light-emitting diodes

Orange-yellow luminescent Y2-xSr1-yAl4SiO12: xCe3+, yMn2+ (x = 0.04–0.06, y = 0.1–0.6, abbreviated as YSAS: xCe3+, yMn2+) phosphors with garnet structure were prepared by the high temperature solid-phase method. The matrix energy band is calculated by DFT, where YAG is 4.535 eV and YSAS is 4.874 eV. The Rietveld refinement of the XRD data indicates that Ce3+ mainly replaces the Y3+ sites, while Mn2+ selectively occupies. The Gaussian peaks of the fluorescence spectrum prove that Mn2+ occupies two luminescent centers, which are further determined by Van Uitert's empirical formula. The doping of Ce3+/Mn2+ units can effectively enhance the structural rigidity of the YAG host and promote the red-shift of the emission peak position of Mn2+. The fluorescence decay kinetics test proves that Ce3+ can transfer energy to Mn2+, and the transfer efficiency reaches 72.08% at y = 0.5. The thermal stability test of the phosphor shows the luminous intensity at 473 K still maintains 86% of the room temperature. The phosphor prepared in this experiment was combined with a blue light chip to make a w-LED device, and the performance showed Ra = 86.1, CCT = 5168 K. The above results show that the emission color of the garnet structure can be tuned by energy transfer, which is attractive for future applications.

Preparation and photoluminescence performance of BaMoO4:Sm3+ orange–red phosphor

In the present paper, orange–red BaMoO4:Sm3+ phosphor was synthesized by high-temperature solid-phase method. The morphology, elemental composition, crystal structure, photoluminescence performance, and charge compensation mechanism of BaMoO4:Sm3+ were investigated. Results indicated that the BaMoO4:Sm3+ phosphor particles were spherical-like in shape with approximate particle size of 2 μm and contained Ba, Mo, O, and Sm elements. The Rietveld-refinement of X-ray diffraction profile of BaMoO4:Sm3+ was consistent with a tetragonal lattice. Under 404 nm excitation of light, BaMoO4:Sm3+ phosphor showed the strongest emission peak at 649 nm and emitted an orange–red light. When the orange–red phosphor was packaged with a 395 nm UV chip and tested, the color coordinates were (0.3109, 0.3626) under a current of 60 mA, the color rendering index Ra = 81.5, and the color temperature was 6385 K. These results indicated that BaMoO4:Sm3+ red phosphor is suitable as a red light component in WLEDs and has potential practical applications.

Preparation and characterization of a new orange-red phosphor Ba2LaTaO6:Eu3+ with abnormal thermal quenching

Herein, double-perovskite Ba2LaTaO6 Eu-doped orange-red phosphors were successfully synthesized using a high-temperature solid-phase method. The phosphor phase purity was investigated using X-ray diffraction and microscopic morphology analyses. Their luminescence properties were investigated using absorption, emission, excitation, and temperature-dependent spectra. The transition mechanism mainly involves a magnetic–dipole transition with an energy transfer mode featuring multipole–multipole interactions, and concentration quenching is achieved via dipole–dipole interactions. In addition, the intensity of the temperature-dependent spectrum increases abnormally between 298 and 373 K, with the luminous intensity at 373 K increasing to 110% of that observed at room temperature. This phenomenon can be attributed to lattice defects in Ba2LaTaO6:Eu3+, and the phosphor luminous intensity at 473 K remains at 80.62% of that at room temperature. In addition, white-light-emitting diode devices based on this novel Ba2LaTaO6:0.35Eu3+ phosphor were fabricated to evaluate the potential applications of the as-prepared phosphor.

Multifunctional rare earth ions-doped Ba2LaF7 nanocrystals for simultaneous temperature sensing and photothermal therapy

As an urgent problem, cancer has boosted the development and application of many treatment technologies in biomedicine. Photothermal therapy with precise control for tumors has gained more and more attention as a promising technology in biomedical fields. In this work, rare earth ions-doped Ba2LaF7 nanocrystals have been successfully developed by the high-temperature solid-phase method as the core material in a multi-functional system. Optical temperature measurement based on fluorescence intensity ratio improves sensitivity by widely separating Er3+ and Nd3+ emission bands. Meanwhile, the relative sensitivity increases with increasing temperature. From the comparison between the fitting curve and the actual temperature, it can be concluded that the nanocrystals have a good photothermal response to the laser pumping power and can even be used for photothermal imaging. On this basis, to study its optical measurement and photothermal conversion performance, we made a multifunctional system acting on biological tissues. The results suggest that the developed material has a potential application in bio-targeted photothermal therapy.

Synthesis and photoluminescence properties of a novel green-emitting LiYGeO4 :Tb3+ long afterglow phosphor.

A new green luminescent phosphor, Li(Y1-x Tbx )GeO4 , was prepared using a high-temperature solid-phase method. The X-ray diffraction (XRD) measured spectrum agreed well with the standard card JCPDS No. 02-3479, indicating that it is a quaternary compound belonging to the space group of Pnma(62) with an orthogonal crystalline phase; the excitation and emission spectra measured using the phosphor spectrometer showed that it can be effectively excited by near-ultraviolet light at 378 nm and blue light at 482 nm, and produced excellent strong emission of green light at 550 nm. The afterglow test results show that the sample had a good long afterglow effect at lower doping concentrations; the thermal stability test results showed that its thermal burst activation energy ΔE ≈ 0.37 eV had its excellent thermal stability. The rare earth Tb3+ -doped green phosphor, LiYGeO4 :Tb3+ , has potential applications in household lighting, medical therapy, and optical storage.

Enhancing battery performance by glucose addition to form spherical Li4Ti5O12 as an anode material

A high specific capacity spherical Li4Ti5O12 anode material of Lithium-Ion battery was successfully synthesized by a high-temperature solid-phase method consisting of ball milling, spray drying and calcination processes. Its suitable reaction conditions were explored by the orthogonal experiment method, and the effect of glucose addition on the morphology and electrochemical performance of Li4Ti5O12 was studied. The addition of glucose could change the surface structure of Li4Ti5O12, improve its conductivity, therefore enhance its electrochemical performance. The prepared lithium titanate represents a superior specific capacity of 163 mAh·g−1 at 0.2 C rates, approximately 65 mAh·g−1 under 10 C rates, and the capacity retention rate of sample remained 97.55% after 100 cycles of charging/discharging process.

Nanorod-sphere hybrid MnOx synthesized by a simple thiourea reduction of MnO2 for long lifespan aqueous zinc-ion batteries

• Nanorod-sphere hybrid MnOx was successfully synthesized by a mild reaction of MnO 2 with thiourea. • A large number of oxygen vacancies was introduced in MnOx to accelerate the electrochemical kinetics. • The as prepared MnOx shows superior cycling stability than the pristine MnO 2 . Although many reports have improved the electrochemical performance from the perspective of changing the nanostructure of MnO 2 , such as the hydrothermal method and high temperature solid phase method, few studies modulate the morphology of MnO 2 at low temperature. In this work, the nanorod-sphere hybrid MnO x with better cycling stability was successfully synthesized by thiourea reduction of low crystallinity MnO 2 . The oxygen defects introduced by thiourea reduction accelerate the electrochemical kinetics and effectively improve its cycle stability. The MnO x exhibits enhanced cycling stability with 78.9% capacitance retention compared with that of pristine MnO 2 (3.9%).

Structure and luminescence properties of Bi3+-doped ZrSiO4 phosphors for near-UV excited white LEDs

• A novel ZrSiO 4 :Bi 3+ phosphor has been synthesized. • The ZrSiO 4 :Bi 3+ samples exhibit broad emission bands peaked at 548 nm when excited at 361 nm. • The ZrSiO 4 :Bi 3+ phosphors own excellent thermal stability. • The luminescence mechanisms and energy transfer processes are discussed. ZrSiO 4 :Bi 3+ phosphors were synthesized by conventional high-temperature solid-phase method. The structural and optical behaviors were investigated by X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy and photoluminescence spectra. Bi 2 O 3 contributes to the ZrSiO 4 phase generation from liquid phase sintering. The ZrSiO 4 :Bi 3+ shows a broad emission band centered at 548 nm when excited at 361 nm. The Bi 3+ doping concentration is optimized to be 4 mol%, and the luminescence intensity of ZrSiO 4 :0.04Bi 3+ at 150 °C keeps 84% of that at room temperature. The results indicate that the ZrSiO 4 :Bi 3+ phosphors offer more possibilities in the near-UV excited white LED applications.

Synthesis and photoluminescence performance of single-component Ca3YAl3B4O15:Dy3+, Eu3+ white-emitting phosphor for white light-emitting diodes

A single-component Ca3YAl3B4O15 (CYAB):Dy3+, Eu3+ phosphor was synthesized by the traditional high temperature solid-phase method, Dy3+ and Eu3+ were codoped in the structure to obtain a warm white emission. The results of XRD and EDS revealed that all samples had the standard Ca3YAl3B4O15 structure, and no impurity phase appeared with codoping. The emission of Dy3+ in CYAB consisted of both main peaks at 476 nm and 570 nm, with which a white emission could be observed. Furthermore, a characteristic emission peak of Eu3+ appeared at 617 nm in Dy3+/Eu3+-codoped samples to supplement red component for the white emission of Dy3+, due to the energy transfer effect between Dy3+ and Eu3+. With the amount of Eu3+ raised, the correlated colour temperature of CYAB:Dy3+, Eu3+ phosphor obviously decreased, and a warm white light was successfully realized from the manufactured w-LEDs. Therefore, all results indicated that the single-component Dy3+/Eu3+ codoped CYAB white-emitting phosphor had a potential application in ultraviolet excited w-LEDs.

Rare earth tungstate high-entropy ceramic powders containing holmium with broad-spectrum antibacterial and antiviral activity

A2W3O12-type (A=La, Sm, Eu, Gd, RE) rare earth tungstate high-entropy ceramic powder with a positively charged surface was fabricated by a high-temperature solid-phase method, and its antibacterial and antiviral properties were evaluated for the first time. Changes in the antibacterial and antiviral activity and ionic solubility of these compounds induced by changing the RE element at the A-position were investigated. The A2W3O12 high-entropy ceramic powder was a stable surface antibacterial material. Its antimicrobial properties are not affected by light and environmental acids and bases. The (La0.2Sm0.2Eu0.2Gd0.2Ho0.2)2W3O12 high-entropy ceramic powder had the best antibacterial performance in the absence of light, and the killing rate was more than 99.9% for both Staphylococcus aureus and Escherichia coli. On this basis, the animal viruses H1N1 influenza virus (enveloped) and EV71 enterovirus (nonenveloped) were selected for antiviral testing, and the survival rate of both viruses decreased by more than 99% within 2 h. The powder was evaluated for ion solubilization under acidic and alkaline service conditions, showing low ion solubilization and superior environmental suitability.

Study on energy transfer mechanism and optical properties of LiLaSiO4: Dy3+, Tb3+ phosphors with excellent thermal stability and color tunability

In this paper, a variety of color-tunable LiLaSiO4: xDy3+, yTb3+ phosphors were manufactured by high temperature solid phase method. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Photoluminescence (PL) were used to characterize the phase, luminescence properties and thermal stability of the samples. In LiLaSiO4: Dy3+ phosphors, the best doping concentration is x = 0.03, corresponding to the pale yellow emission band. In LiLaSiO4: Dy3+, yTb3+ (y = 0–0.06) phosphors, energy transfer can be verified and the energy transfer mechanism are discussed in detail. In addition, by adjusting the concentration ratio of Dy3+/Tb3+ in LiLaSiO4 phosphors, the color tuning from pale yellow to green was realized. Finally, we also study its thermal stability, the activation energy (ΔE) is −0.1483 eV. Current research shows that Dy3+, Tb3+ co-doped LiLaSiO4 phosphors have wide application potential in fluorescent display devices.