High-temperature Solid-phase Method Research Articles

Synthesis and luminescence properties of Dy3+ and Tb3+ doped Y2Mg3Ge3O12 phosphors with excellent thermal stability and color tunable emission

A series of Y2-x-yMg3Ge3O12: xDy3+, yTb3+ samples were manufactured by high temperature solid phase method. XRD test and Rietveld refinement clarified the phase purity of the samples. When the excitation wavelength is 352 nm, the energy transfer efficiency is 57.74%, and q-q interaction is the main energy transfer mechanism of Dy3+-Tb3+ co-doped samples. In addition, we tested the thermal stability of Y1.94Mg3Ge3O12:0.05Dy3+, 0.01 Tb3+ sample, and found that its luminous intensity at 423 K could still reach 93.86% of that at 303 K. By changing the concentrations of Tb3+, the luminescent color of the samples could also be changed from blue-white light to yellow-green light. These results indicate that Y2Mg3Ge3O12 co-doped with Dy3+ and Tb3+ is expected to be applied in the field of white light LEDs.

Tunable Luminescence of Ce3+/Eu2+ Activated in Single-Phase Li2BaSiO4 Phosphor via Energy Transfer

A series of Ce3+,Eu2+ co-doped Li2BaSiO4 cyan-green phosphors were synthesized by a high temperature solid phase method. The crystal structure, morphology, luminescent properties and temperature characteristics of the corresponding samples were systematically studied. The main peaks of the emission spectra of Li2BaSiO4:Ce3+,Eu2+ were shifted from 400 nm to 500 nm by adjusting the Ce3+,Eu2+ co-doping concentration. And a series of phosphors with continuous changes from blue to cyan green were obtained, which effectively compensated for the gap between the white LED at 470–510 nm region. The energy transfer efficiency and mechanism of Ce3+,Eu2+ in Li2BaSiO4 were studied by fluorescence lifetime. The highest energy transfer efficiency was 46.01%, and the energy transfer mechanism was determined to be electric dipole-electric dipole transition. Finally, fabricating a white LED device which coated blue, green-yellow, red and as-prepared cyan phosphors on the surface of ultraviolet chip (350 nm), and the device exhibited excellent luminescence characteristics (Ra = 95.2, CCT = 3105 K). The results show that the Li2BaSiO4:Ce3+,Eu2+ phosphor developed can be regard as single-component tunable color luminescent materials under the excitation of near ultraviolet light.

Effects of Lithium Salt Addition Methods on the High-Temperature Electrochemical Performance of LiMn2O4

The poor high-temperature stability of spinel LiMn2O4 cathode material has become a bottleneck hindering its large-scale application. To enhance its high-temperature electrochemical performance, the effects of two different methods of lithium salt addition on its high-temperature electrochemical performance were studied. Two methods, Li+ infiltration and solid phase mixing, were used to prepare spinel LiMn2O4 cathode material by the same high-temperature solid phase method, respectively. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, Raman, and particle size analysis. Electrochemical performance tests were carried out on the electrochemical equipment by assembling into a half-battery. The results show that the material obtained by the lithium salt solid phase mixing method presents a loose structure composed of small primary particles to form a spherical secondary particle. However, the material obtained by the Li+ infiltration method presents an octahedral crystal structure, showing a trend toward single crystal. At the same time, its calcination time is greatly shortened (from 26 to 6 h) at the same calcination temperature. The electrochemical performance test results at 55 °C show that the LiMn2O4 prepared by Li+ infiltration has a better high-temperature electrochemical performance.

GAGG:Cr<sup>3+ </sup>Phosphors for Far-Infrared Light Emitting Diodes

Recently, Far-infrared Light Emitting Diodes have attracted considerable interest in the research field worldwide. Emerging light therapy requires effective red/far-infrared light resources in clinical and plant photomorphogenesis to target or promote the interaction of light with living organisms. Here, Gd3Al4GaO12:Cr3+ (hereinafter referred to as: GAGG:Cr3+) phosphor was synthesized by high-temperature solid-phase method, and the crystal structure, morphology, and luminescence properties of this series of phosphor samples were studied. Through X-ray powder diffraction to obtain pure phase GAGG:Cr3+ series phosphor. Under the excitation of 420nm blue light, a broad band emission from 640 to 850nm is obtained, which is the result of the transition of Cr3+ 4T2→4A2 level. A sharp emission peak at 693nm is the R line belonging to Cr3+ in Gd3Al4GaO12 garnet. R line is assigned to the spin-forbidden 2E→4A2 transitions of Cr3+ ions that occupy the ideal octahedral sites. As the Cr3+ doping concentration increases, the luminous intensity of the sample increases first and then decreases. When the doping concentration of Cr3+ is 0.1mol phosphor,the luminous intensity is strongest at one single broad peak at about 712nm. At 440k, the R sharp line (693nm) and broad band (712nm) emission intensity maintained 78.6% and 71.8% , compared to room temperature intensity, respectively. The change of fluorescence lifetime at different temperatures gives the mechanism of fluorescence change with temperature. The current exploration will pave a promising way to engineer GAGG:Cr3+ activated optoelectronic devices for all kinds of photobiological applications.

Theoretical Calculation of Bond Energy, Self-Reduction Phenomenon, and Photoluminescence Properties of Eu/Ce Single-Doped and Codoped Ba2CaB2Si4O14 Phosphors

The self-reduction of Eu3+ to Eu2+ and Ce4+ to Ce3+ can first be found by doping rare earth ions RE (RE = Eu, Ce) in Ba2CaB2Si4O14 (BCBSO). The Eu2+/Eu3+ codoped BCBSO and Ce4+/Ce3+ codoped BCBSO and Eu/Ce codoped BCBSO were synthesized by a high-temperature solid-phase method in air and reducing atmospheres, respectively. By comparing the photoluminescence spectra in air and reducing atmospheres, the self-reduction phenomenon of Eu3+ and Ce4+ in the BCBSO were verified adequately. The theoretical method of the bond energy was used to analyze the occupancy and self-reduction of Eu or Ce ions. The experimental results are in agreement with the theoretical ones. The color tuning phosphors were achieved in BCBSO:Eu and BCBSO:Ce. The codoped system BCBSO:Eu, Ce was studied and it was found that the position and shape of the emission spectra changed with the change in the excitation wavelength, and the change in the corresponding color could be seen from the CIE chromaticity coordinates. Its emission peak shifts from 481 to 595 nm with the increase in the Ce3+ concentration in the codoped system under the excitation of 365 nm. Based on the fluorescence lifetime, the energy transfer process between Eu2+–Ce3+ is proved, and its emission color can be adjusted to a certain extent.

Fabrication of a new self-assembly compound of LiTaMoO6 with cationic manganese porphyrin utilized as an ascorbic acid and dopamine sensor

A novel highly selective nanocomposite MnTMPyP/TaMoO6 was successfully synthesized and developed for simultaneous detection of Ascorbic acid (AA) and dopamine (DA). Firstly, the host material LiTaMoO6 was synthesized by the high temperature solid phase method. After the exfoliation/restacking process of the host material, the nanocomposite was formed through electrostatic self-assembly. The structure and morphology were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer analysis (EDS), ultraviolet-visible (UV–vis) and Fourier transform infrared spectrometer (FTIR). And the electrochemical behaviors of the modified electrode were further explored by cyclic voltammetry (CV), electrochemical impedance analysis (EIS), and differential pulse voltammetry (DPV). Under the optimal conditions, the MnTMPyP/TaMoO6 provides a high sensitivity and selectivity in detecting AA and DA with linear response ranges of 12–674 μM. The resulting detection limit is also calculated as 0.97 and 0.54 μM, respectively. In addition, the MnTMPyP/TaMoO6 nanocomposite exhibits excellent stability, reproducibility, and good anti-interference.

Preparation and electrochemical study of PVDF-HFP/LATP/g-C3N4 composite polymer electrolyte membrane

Li1.3Al0.3Ti1.7(PO4)3 powder (LATP) is synthesized by high temperature solid phase method, and then a composite polymer electrolyte membrane Poly(Vinylidene Fluoride-Hexafluoropropylene)/LATP/graphitic-C3N4 is prepared by a simple casting method. Then, the influence of porous layered g-C3N4 on the composite polymer electrolyte membrane is studied by morphology characterization and electrochemical measurement. The experimental results show that the addition of g-C3N4 improves the ionic conductivity (2.55 × 10-5 S cm−1) and lithium ion transference number (0.647) of the composite polymer electrolyte membrane (CPE), and the CPE membrane PVDF-HFP/LATP/g-C3N4 has a broad electrochemical window (up to 5.0 V) and superior electrochemical stability.

Study on the color tunability and energy transfer mechanism in Tm3+/Dy3+ co-doped LiLaSiO4 phosphors

Many color-tunable LiLaSiO4: αTm3+, βDy3+ phosphors were prepared using the traditional high-temperature solid-phase method. The phase composition, surface morphology, fluorescence spectrum, fluorescence lifetime, energy transfer mechanism, and color coordinates of the samples were analyzed using XRD, SEM, TEM and fluorescence spectrometer. The results show that LiLaSiO4: αTm3+ phosphor emits high intensity blue light at 460 nm and the concentration quenching point of Tm3+, α = 0.015 mol. In LiLaSiO4: αTm3+, βDy3+ phosphors, as the doped Dy3+ doping increases, the luminescence intensity of Tm3+ gradually decreases, the luminescence intensity of Dy3+ first increases and then decreases. The concentration quenching point of Dy3+, β = 0.015 mol. Adjustable light-emitting color can be obtained by changing the doping molar mass of Dy3+ or the wavelength of the excitation light. There is an effective energy transfer between Tm3+→Dy3+. The energy transfer mechanism is the electric dipole-electric dipole interaction, and the energy transfer efficiency reaches 90.11% when β = 0.06 mol. The quantum yield of LiLaSiO4:0.015 Tm3+,0.015Dy3+ was 39.0%. The single-matrix white light LiLaSiO4: αTm3+, βDy3+ phosphors with excellent performance is a prospective material for of white LEDs.

Garnet type Y2Mg3Ge3O12: Dy3+ / Eu3+ phosphors excited near ultraviolet: Luminescence properties and energy transfer mechanisms

A battery of Dy3+ single-doped and Dy3+/Eu3+ co-doped Y2Mg3Ge3O12 phosphors were manufactured by high-temperature solid-phase method. The XRD patterns were tested and Rietveld refined. When the samples were excited by 352 ​nm near ultraviolet light, the energy transfer efficiency can reach 83.2%, and the energy transfer mechanism is electric dipole-electric dipole interaction. The thermal stability of Y1.75Mg3Ge3O12:0.05Dy3+, 0.2Eu3+ was tested. When the temperature reached 150 ​°C, its luminous intensity droped to 92.4% of the initial temperature (30 ​°C). By changing the concentrations of Eu3+, white light with red light can be obtained. The above results indicate that these samples are expected to become candidate materials in the domain of solid-state lighting.

A Review on Luminescent Rare Earth Complexes

At present, rare earth elements are widely used in various industries. In this paper, luminescent rare earth complexes are taken as a starting point to explore the luminescence principles of several important rare earth elements. The commonly used synthesis methods of luminescent rare earth complexes in recent year are also summarized, mainly including co-precipitation method, high temperature solid phase method, sol-gel method and hydrothermal synthesis method. And prospects for the future research on luminescent rare earth complexes are made.

Preparation and electrochemical hydrogen storage application of mesoporous carbon CMK-3 coated Co2B alloy composite

Mesoporous carbon CMK-3 is synthesized using mesoporous molecular sieve SBA-15 as the template. Co2B alloy is prepared by the high temperature solid phase method. Composites of Co2B mixed with 2%, 5%, 7% and 10% of CMK-3 are fabricated via ball-milling to improve the electrochemical performance of Co2B alloy. Ultimately, the discharge capacity reaches a maximum (662.8 mAh/g) for 5% doping amount of CMK-3. The CMK-3/Co2B composite materials exhibit preferable HRD and improved corrosion and oxidation resistance. CMK-3/Co2B displays excellent electrochemical and kinetics properties owing to the unique electrocatalytic activity and structural feature of CMK-3, which can accelerate the hydrogen transmission.

Research on a new type of near-infrared phosphor Li2MgZrO4:Cr3+- synthesis, crystal structure, photoluminescence and thermal stability

Abstract Broadband NIR phosphors are urgently needed in NIR-LED and medical imaging. In this paper, a new type of near-infrared phosphor Li2Mg1-0.5xZr1-0.5xO4: xCr3+(0.6% ≤ x ≤ 1.6%) was synthesized by high temperature solid phase method. The optimal doping concentration of the phosphor is x = 1.0%, which exhibits broadband emission in the range of 600–1200 nm, and reaches the full width at half maximum (FWHM) of 205 nm under 462 nm blue excitation. The X-ray diffraction characterization results of the Li2Mg1-0.5xZr1-0.5xO4: xCr3+(0.6% ≤ x ≤ 1.6%) sample are refined and analyzed, and the doped sample is basically consistent with the pure phase. The sample was characterized by diffuse emission, and it was found that the sample matrix had intrinsic absorption. The thermal stability of Li2Mg0.995Zr0.995O4:1.0%Cr3+ phosphor was studied, and its relative intensity was 51.3% of room temperature at 100 °C. The results show that this new type of ultra-wide near-infrared emitting phosphor has application potential in medical imaging and PC-LED directions.

Dual-emitting from Bi3+/Eu3+ co-activated akermanite phosphor for optical thermometric applications

In this paper, Ca 2 MgSi 2 O 7 : Bi 3+ , Eu 3+ thermometric phosphors with dual-emitting centers were favorably designed. Phosphors were created by the approach of solid phase in high temperature condition. The inner phase structure and photoluminescence characteristics were investigated. The approaches of characterization including X-ray diffractometry, SEM, EDS mapping, ultraviolet–visible diffuse reflectance spectroscopy, as well as fluorescence spectrometry were applied. The influence of temperature on the photoluminescence characteristics of Ca 2 MgSi 2 O 7 : Bi 3+ , Eu 3+ phosphors was systematically researched. The intensity ratio of 3 P 1 → 1 S 0 purple luminescence of Bi 3+ and 5 D 0 → 7 F 2 red luminescence of Eu 3+ is dependent on the temperature, which provides a method of optical sensing thermometry. Under the UV excitation of 287 nm, the maximum relative sensitivity ( S r ) of this Ca 2 MgSi 2 O 7 : Bi 3+ , Eu 3+ phosphor is 0.66%K −1 (at 533 K) and absolute sensitivity ( S a ) gets to 0.0086 K −1 (at 573 K). The experimental phenomena were explained by the thermal-quenching mechanism. The garnered results provide an idea for the future development of luminescence intensity ratio (LIR) technology sensing materials on the basis of Ca 2 MgSi 2 O 7 . 1 The novel Ca2MgSi2O7: Bi3+, Eu3+ phosphors with dual-emitting centers were prepared by high-temperature solid-phase method in air. 2 The Ca2MgSi2O7: Bi3+, Eu3+ phosphors can circumvent the drawbacks of TCL-based phosphors. 3 The Ca2MgSi2O7: Bi3+, Eu3+ phosphors have high temperature sensitivity and signal discriminability. 4 The thermal-quenching mechanism of Bi3+ and Eu3+ were discussed.

Double perovskite structure CaLaMgTaO6: Bi3+, Eu3+ co-doped phosphors for optical temperature measurement

A series of new double perovskite structure CaLaMgTaO6: Bi3+, Eu3+ phosphors were synthesized by high-temperature solid-phase method. The crystal structure, luminescence characteristics and temperature sensing performance have been systematically studied. The substitution rule of Bi3+ in CLMT and its luminescence characteristics are described. The decay curve of Bi3+ further proves the existence of an energy transfer from Bi3+ to Eu3+. They have different thermal quenching behaviors, and their fluorescence intensity ratio (FIR) parameter has tremendous temperature sensing performance. Under 329 nm ultraviolet excitation, the emission peaks at 408 nm and 614 nm are used as the reference signal, the largest absolute sensitivity is 0.0127 K−1 at 573 K, and the maximum relative sensitivity is 1.33%K−1 at 483 K. This indicates that CaLaMgTaO6: Bi3+, Eu3+ is a material with excellent temperature measurement performance and applicability in non-contact optical thermometers.

Full-visible-spectrum emission with high color rendering index and low correlated color temperature enabled by a single-phased phosphor of α-Sr2V1.98P0.02O7: 0.5% Eu3+

A single-phased warm white phosphor of α-Sr2V1.98P0.02O7: 0.5 % Eu3+ with low correlated color temperature (CCT) and high color rendering index (CRI) was synthesized by high temperature solid phase method. By changing the ratio of PO43−/VO43−, the emission intensity of VO43− and the energy transfer efficiency of VO43−→Eu3+ can be effectively tuned, and the full-spectrum warm white light emission of phosphors in the range of 400−700 nm can be realized. Moreover, the temperature-dependent emission spectra and thermal quenching properties were investigated in detail. On this basis, the WLED prototype devices were packaged with the synthesized phosphors α-Sr2V1.98P0.02O7: 0.5 % Eu3+ and 365 nm near-ultraviolet (NUV) chips and high-quality warm white light emission with CCT = 3188 K and CRI Ra = 93.5 were achieved. These findings provide new insights into exploring single-phased white phosphors for NUV-pumped warm w-LEDs with high CRI property and low CCT value.

Effects of Ni2+, Zr4+, or Ti4+ doping on the electromagnetic and microwave absorption properties of CaMnO3 particles

Although CaMnO3 has been widely studied and used for its thermoelectric properties and giant magnetoresistance effect, little information exists about its application for microwave absorption. In this study, we synthesized CaMnO3, CaNi0.05Mn0.95O3 CaTi0.05Mn0.95O3 and CaZr0.05Mn0.95O3 with an orthorhombic system using a simple high-temperature solid-phase method. The minimum reflection loss value and effective absorption bandwidth could be efficiently improved due to the enhanced match complex permittivity produced after the Ni, Ti or Zr ions were substituted for Mn ions in CaMnO3. The minimum reflection loss value increases to −39.7 dB from −14.1 dB and the effective absorption bandwidth increases to 4.9 GHz from 2.7 GHz. The magnetic loss results only in a negligible influence on the microwave absorption. The enhancement of microwave absorption properties was primarily due to the stronger polarization effect. When Ni2+, Ti4+, or Zr4+ is introduced in the CaMnO3 lattice, the charge balance is broken, and the crystal lattice distortion increases because of the substitutive ions, interstitial ions, oxygen vacancy and exchange effect of Mn3+~Mn4+. The results indicate that CaMnO3 with reasonable doping at the Mn-site could achieve excellent microwave properties of wide bandwidth, high-efficiency absorption, and adjustable response frequency.

The preparation, electrochemical properties, Na+ migration mechanism and kinetics of a new anode material Na4TiO(PO4)2 with open framework for Na ion batteries

A new anode material for NIB Na4TiO(PO4)2 and the carbon coating counterpart Na4TiO(PO4)2/C, which were never reported elsewhere, were synthesized by a traditional high-temperature solid-phase method and explored both experimentally and theoretically. The morphology and the composition of Na4TiO(PO4)2 and Na4TiO(PO4)2/C were examined by XRD, SEM, TEM, ICP, EDS and XPS. Na4TiO(PO4)2/C material shows better rate capability and cycle stability than Na4TiO(PO4)2. It provided an initial charge and discharge capacity of 117/234.5 mAh g−1 at a current rate of 1C, and retained a capacity of 103/107.4 mAh g−1 after 240 cycles. Except the initial several cycles, the Coulomb efficiencies of Na4TiO(PO4)2/C were higher than 95%. When the current density experienced 0.1 C, 0.2 C, 0.5 C, 1 C and 2 C and returned to 0.1 C, the discharge capacity of 149.29 mAh g−1 can be obtained by the Na4TiO(PO4)2/C electrode, closed to the initial 171.12 mAh g−1. The chemical diffusion coefficient in discharge process varies from 1.3 × 10−9 to 2.6 × 10−9 cm2 s−1 and from 9.2 × 10−10 to 4.9 × 10−9 cm2 s−1 for charge process, showing features of fast ion conducting materials. Both nudged elastic bands (NEB) method and molecular MD show a relatively low diffusion barrier of ca. 0.4 eV on a-c plane and a 0.1 eV higher energy barrier along b-axis. The theoretical calculations show that the high mobility of Na+ originates from the ample cavities and the complicated three dimensional conducting framework in the lattice. Ex-situ experiments reveal an ultra-stable framework of Na4TiO(PO4)2 material in the intercalation/deintercalation process and also a less than 0.92% contraction in this process.

High quality upconversion luminescence and excellent thermal stability of Yb3+, Er3+ codoped Sr3NaY(PO4)3F phosphors

A series of Sr3NaY(PO4)3F (SNYPF): Yb3+, Er3+ phosphors were synthesized by high temperature solid-phase method. The green and red emission region of SNYPF: Yb3+, Er3+ in the upconversion luminescence (UCL) spectra consist of two distinctly separated peaks under 980 nm laser excitation, which can be assigned to the transition from 2H11/2, 4S3/2 and 4F9/2 to 4I15/2 of Er3+. The SNYPF: Yb3+, Er3+ phosphors possess significant optical temperature sensing feature with the maximum sensitivity value of 0.00312 K−1 (464 K) and 0.00272 K−1 (209 K), as well as 0.00242 K−1 and 0.00244 K−1 at 300 K for green and red emission, respectively. Notably, the intensity of green emission remains almost unchanged with the increasing of temperature, indicating the excellent thermal stability of the phosphors. The above results demonstrate that SNYPF: Yb3+, Er3+ is a potential UC phosphor, which is suitable for optical temperature sensing.

Research on a persistent red tone fluorescent polyacrylonitrile fiber with coaxial structure based on Sr2MgSi2O7:Eu2+, Dy3+ and Y2O2S:Eu3+, Mg2+, Ti4+

In order to obtain a red fluorescent fiber with long persistent performance, Sr2MgSi2O7:Eu2+, Dy3+ and Y2O2S:Eu3+, Mg2+, Ti4+ phosphors were prepared by high-temperature solid-phase method, then the phosphors and Rhodamine B were spun into the Polyacrylonitrile (PAN) through coaxial wet-spinning. The structure and morphology of samples were characterized by the X-ray diffraction, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and particle size analyzer. Fluorescent properties were studied based on photoluminescence spectroscopy and afterglow decay curve. The data show that Sr2MgSi2O7 has blue broadband emission due to the electronic transition of Eu2+, and the Y2O2S has red linear emission spectrum because of the electronic transition of Eu3+.The analysis results reveal that the excellent afterglow performance of Sr2MgSi2O7 plays a significant role in the secondary excitation. Rhodamine B was added in the coaxial fiber as a red light compensator through transferring the blue light to red fluorescence.

Effect of Li+ doping on the luminescence performance of a novel KAlSiO4:Tb3+ green-emitting phosphor

A new green-emitting phosphor, KAlSiO4:1.5 mol% Tb3+, x mol% Li+, was prepared via a high-temperature solid-phase method, and its crystal structure, diffuse reflectance spectrum, and luminescence were studied. The results show that the Li+ doping shifts the strongest diffraction peak to a high angle direction, reducing grain size by 11.4%. The entry of Li2CO3 improves the luminescence performance of KAlSiO4:1.5 mol% Tb3+. At a Li+ concentration of 1.5 mol%, the sample has strong absorption in the ultraviolet light range from 250 to 400 nm. The luminous intensity of the sample at 550 nm approximately quadruples after Li+ doping. Additionally, the colour purity of the sample and the internal quantum yield increase to 83.3% and 42%, respectively. The sample changes colour with time when exposed to air without an obvious fading phenomenon. The emission intensity at 200 °C is 95.1% of its value at room temperature, indicating that the phosphor has excellent thermal stability when x = 1.5. These results show the feasibility of using the silicate phosphor for generating the green light component of white light-emitting diodes for solid-state lighting.