High-temperature Solid-state Process Research Articles

Synthesis, properties, and applications of all-solid-state reference electrode based on AgTi2(PO4)3

High-density AgTi2(PO4)3 as a solid electrolyte was synthesised by a high-temperature solid-state process. The optimal sintering temperature was determined to obtain the best structural and electrical performance. Based on the as-prepared AgTi2(PO4)3 fast-ion conductor, a new type of all-solid-state reference electrode was prepared, and its electrochemical properties, such as cyclic voltammetry curves and potentials at varying pH, were investigated. A pH sensor was designed by combining an AgTi2(PO4)3 reference electrode with an Ir/IrO2 pH electrode. This pH sensor exhibited a good linear response to pH values in aqueous solutions and simulated seawater samples. In addition, a metal ion sensor, comprising the as-fabricated solid-state reference electrode, a Pt counter electrode, and a glassy carbon working electrode, was employed to quantify Cu2+, Hg2+, and Pb2+ concentrations using differential-pulse anodic stripping voltammetry. The resulting peak currents correlated with the metal ion concentrations and exhibited a low detection limit, good linearity, and wide detection range, which is suitable for performing chemical analysis in harsh marine environments.

Charge compensation effect of alkali metal ions on luminescence enhancement and negative thermal quenching of Sr1-xLaNaTeO6:xEu3+ red phosphors

A series of novel phosphors, specifically Eu3+-doped and Eu3+/M+ co-doped (M = Li+, Na+, K+) SrLaNaTeO6, were synthesized via a high-temperature solid-state process. The luminous properties and thermal stability of these phosphors were thoroughly investigated. When subjected to the appropriate excitation wavelengths (395 and 465 nm), all phosphors demonstrate a pronounced red light emission, corresponding to the 5D0→7F2 transition of Eu3+. The researchers found that the most effective concentration of Eu3+ doping in the Sr1-xLaNaTeO6:xEu3+ phosphor was discovered to be x = 0.25. It was shown that excessive doping leads to concentration quenching, which can be attributed to the energy transfer interaction between Eu3+ ions. The incorporation of Li+, Na+, and K+ as charge compensation ions in conjunction with Eu3+ in Sr0.75LaNaTeO6:0.25Eu3+ phosphor leads to a notable enhancement in light intensity. Notably, the phosphor co-doped with Na+ exhibits the highest luminous intensity among the alkali metal charge compensation ions. The near proximity of the ion radius of the charge compensation ion Na+ to that of Sr2+ in the host facilitates the occupation of the Na + ion in the Sr2+ lattice location. Sodium ions (Na+) have the ability to counteract the positive defects resulting from the substitution of europium ions (Eu3+) with strontium ions (Sr2+), hence maintaining charge neutrality. Additionally, it should be noted that Sr0.5LaNaTeO6:0.25Eu3+,0.25Na+ phosphor exhibits a remarkable quantum yield of 71.26 % and lacks thermal quenching. These characteristics suggest that this particular phosphor holds promising potential for utilization in developing white-light-emitting diodes.

A single phase Li2Ba5W3O15:Dy3+/Eu3+ phosphor for color tunable devices and non-contact optical thermometry

A set of warm white phosphor samples Li2Ba5W3O15 (LBW):xDy3+, yEu3+ were prepared via a high-temperature solid-state process. Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray analysis (EDX) with X-ray diffraction (XRD) are the structural analyses that show the incorporation of Dy3+ and Eu3+ ions into the LBW host matrix, without causing any damage to the lattice structure. Fourier Transform Infrared Spectroscopy (FT-IR) approves the presence of distinct vibrational characteristics of the proposed phosphors. The band gaps of the prepared phosphor samples were determined using diffused reflectance spectral (DRS) data. The energy transfer between Dy3+ and Eu3+ ions was observed, contributing to the adjustable luminescence of the LBW:Dy3+/Eu3+ phosphors. By varying the activator doping levels while keeping the excitation wavelength constant, the emission colors of LBW:Dy3+/Eu3+ phosphors shift from natural white with negligible color purity to a relatively pure orange-red region. The decay curves follow the bi-exponential behavior of decreasing lifetime with increasing concentration of the activator ions. A temperature measurement model using fluorescence intensity ratio (FIR) was developed using D3E0.75 phosphor demonstrating excellent optical temperature measurement properties, with a maximum value of Sr (=0.97 % K−1). Therefore, all the experimental results indicate that the prepared Dy3+/Eu3+ co-doped LBW phosphors can be a suitable choice for UV-excitable warm white lighting devices with color tunability and non-contact optical thermometry measurements.

Luminescent properties of Sr0.96La0.01MoO4: 0.02Dy3+ yellow phosphors for white light

The yellow Sr0.96La0.01MoO4: 0.02Dy3+phosphors for white LEDs were synthesized by the high-temperature solid-state process, and the samples were analyzed using an X-ray diffractometer and fluorescence spectroscopy. The results indicate that Sr0.96La0.01MoO4: 0.02Dy3+phosphor can be effectively excited by a 352 nm laser and emission by a 573 nm laser. The CIE chromaticity coordinates of Sr0.96La0.01MoO4: 0.02Dy3+phosphor were found in the yellow region with a CCT of 4192 K. The temperature dependency of Sr0.96La0.01MoO4: 0.02Dy3+phosphor under the excitation of 352 nm and the temperature quenching in the emission were detected. The phosphor intensity of the sample reaching the highest level at 573 nm when the x of La3+ equals 0.02. With the increase of the doping concentration of La3+, the color coordinate of the sample excited by UV light moves to the yellow light area. Then we conducted theoretical calculations on the band structure, density of states, and optical properties by the first principle method.

White afterglow observed in Ce3+, Eu2+ and Dy3+ Co-activated Sr3Al2O5Cl2 phosphor

A white phosphor, Sr3Al2O5Cl2: Ce3+, Eu2+ and Dy3+, was synthesized successfully through high temperature solid state process. XRD refinement revealed that all the doping cations replaced the original Sr2+ site in the phosphor lattice. Upon ultraviolet excitation, the phosphor displayed a blue emission from the 5 d-4f Ce3+ transition centered at 441 nm, as well as a broad orange emission from the 5 d-4f Eu2+ transition centered at 636 nm. By adjusting the concentrations of Eu2+, a white emission was achieved with the formula Sr3Al2O5Cl2: 0.005Eu2+, 0.02Dy3+, 0.005Ce3+. After the removal of excitation, a persistent white afterglow was observed due to the presence of Dy3+ electron traps in the lattice with optimal trap depth. The mechanism proposed suggests that the recombination between thermally released electrons originating from the trap center and existing holes at the emission centers of Ce3+ and Eu2+ drives the observed white afterglow phenomenon. These findings highlight the potential of Sr3Al2O5Cl2: Ce3+, Eu2+ and Dy3+ phosphors in solid-state lighting applications.

Synthesis and up-conversion luminescence of Ho3+ and Yb3+ co-doped La7P3O18 phosphors

Ho3+ and Yb3+ co-doped La7P3O18 up-conversion phosphors were prepared by a high-temperature solid-state process. XRD results reveal that the samples are mixtures of monoclinic structure La7P3O18 crystals with P21/n space group and minor LaPO4 crystals. UV—Vis DRS results indicate that La7P3O18 crystal is an indirect semiconductor with an optical band gap of 4.10 eV. After 980 nm laser excitation, the Ho3+ and Yb3+ co-doped La7P3O18 phosphors show the characteristic blue (486 nm), green (550 nm), and red (661 nm) luminescence peaks of Ho3+ ions. The peak at 661 nm dominates in the up-conversion luminescence spectra of samples. Meanwhile, with the increase of Ho3+ and Yb3+ doping content, the up-conversion luminescence intensity increases first and then decreases. By increasing the doping contents of Ho3+ and Yb3+ up to 1 at.% and 10 at.%, respectively, concentration quenching may appear by an electric quadrupole– electric quadrupole interaction process. The pumping power dependence of luminescence indicates that the green and red emissions of samples are excited by a two-photon absorption process. The color coordinates of Ho3+ and Yb3+ co-doped La7P3O18 crystals locate in the orange—red region.

Thermionic Emission Capability of the Ba–Sc–Al–O Compound Synthesized by High-Temperature Solid-State Process

The dibarium scandium aluminum oxide (Ba2ScAlO5) is an important compound for thermionic emission in high-power vacuum devices. Herein, the high-temperature solid-state synthesis mechanism is investigated extensively to develop single-phase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ba2ScAlO5 and evaluate its emission capacity. Barium carbonate, scandium oxide, and aluminum hydroxide are adopted as the reactants. The synthesis temperature, the intermediate phases, and the cell parameters of the final products differ from sintering the coprecipitated precursor. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ba2ScAlO5 single-phase material can be obtained based on the nonstoichiometric mole ratio of BaO:Sc2O3:Al2O3 = 4.4:1.1:0.9. The X-ray Rietveld refinement reveals that the substitution of Sc for Al and the defects of the Ba, Sc, and O vacancies account for the nonstoichiometry and the shrinkage of cells. The test cathode impregnated with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ba2ScAlO5 doped with Ca2+ exhibits an emission capability of 6.79 A/cm2 at 900 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ }\text{C}_{\text {B}}$ </tex-math></inline-formula> in the dc mode. This work demonstrates the feasibility of obtaining <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ba2ScAlO5 with considerable emission through the high-temperature solid-state process.

Tailoring afterglow properties of polychromatic long-persistent LiMg Sr4--2(BO3)3: y Eu2+ phosphor by codoping with Dy3+ or Nd3+

Herein, redshifted long persistent LiMgxSr4-x-2y(BO3)3: y Eu2+, Dy3+(Nd3+) phosphors are successfully prepared in a reducing atmosphere using a high-temperature solid-state process. The emission of phosphors displays redshift characteristics between 633 and 660 nm with an increase in the concentration of Mg2+ substitution, primarily attributed to enhanced energy level splitting of Eu2+ after Mg2+ replacement. The afterglow performance of LiMg0.6Sr3.4-2y (BO3)3: y Eu2+, Dy3+ (Nd3+) samples is enhanced with increase in concentrations of the doped rare-earth ions. An optimal concentration of 6%, the best afterglow performance was achieved because high concentration traps with suitable energy levels were developed; this was confirmed using afterglow measurements and thermoluminescence tests. The Nd3+ codoped phosphor shows improved afterglow performance compared with the Dy3+ codoped phosphor at the same doping concentration, which can be attributed to Nd3+ can easily be incorporated into the borate lattice that generates electron traps with high concentration.

Photoluminescence and afterglow behavior of a new orange long-lasting borate phosphor Eu2+, Dy3+: NaSr4(BO3)3

A new long-lasting phosphor Eu2+, Dy3+: NaSr4(BO3)3 was obtained by high temperature solid state process. The phosphor displays typical 5 dd-4f transition of Eu2+ upon UV illumination with a broad emission centering around 588 nm, which is orange visible to the naked eye. Such an emission can be divided into 2 single emissions since the Eu2+ cations are located in two different crystallographic sites in the forms of [EuO6] and [EuO8]. An optimal doping concentration for Eu2+ cation is determined as 2 at% due to the quenching effect with increasing Eu2+ concentration. The critical distance between the luminescence center is determined around 14 Å. Afterglow behaviors are further observed for the prepared phosphors, which can be expressed by an empirical double exponential decay model. The sample 2% Eu/Dy: NaSr4(BO3)3 displays the best afterglow performance. The reason for such an afterglow performance is revealed by thermal stimulated luminescence (TSL) that the co-doped Dy cations offer large numbers of electron traps with suitable trap depth.

Improved thermal stability and luminescence properties of SrSi2O2N2:Eu2+ green phosphor by a heterogeneous precipitation protocol for solid-state lighting applications

The SrSi2O2N2:Eu2+ green-emitting phosphor, as a member of oxynitride phosphors, could greatly enhance the color quality of the white-light conversed by single yellow-emitting phosphor. However, SrSi2O2N2:Eu2+ phosphors prepared by traditional solid-state ways normally consist hard agglomerates with unevenly dispersed particles and therefore suppress the luminescence properties. This research proposes a heterogeneous precipitation protocol where precipitation process is introduced, in order to produce a precursor in the first phase. And in the second phase, a high-temperature solid-state process is adopted for obtaining the final product. The main results show that, for an optimized SrSi2O2N2:Eu2+ phosphor prepared using our protocol, (1) the SrSi2O2N2:Eu2+ particles are faceted and with smooth faces and (2) the phosphor photoluminescence, external quantum efficiency, stability against thermal exposure, and physical stability consistently outperform the current commercially used product. This research essentially provides an economic way for production of solid-state lighting with enhanced color quality.

Novel high-efficiency up-conversion luminescence of Er3+ doped LiYbW2O8 phosphors for optical temperature sensing investigation

A novel series of Er3+ doped LiYbW2O8 phosphors were synthesized by high-temperature solid-state process. Upon 980 nm NIR laser excitation, the up-conversion emission spectra show that the intense green emissions and weak red emissions can be proposed as the transitions of 2H11/2→4I15/2, 4S3/2→4I15/2, 4F9/2(2)→4I15/2 and 4F9/2(1)→4I15/2 of Er3+ ions, respectively. The optical temperature sensing properties were carefully investigated on the basis of fluorescence intensity ratio (FIR) technology about energy level transitions of 2H11/2→4I15/2 and 4S3/2→4I15/2 in the range from 300 K to 500 K. Moreover, the maximum values of relative sensitivity (Sr) and absolute sensitivity (Sa) are separately about 1.62% K−1 at 300 K and 0.64% K−1 at 500 K, which can prove that the sensitivity of LiYbW2O8:Er3+ is superior to the latest reported materials for temperature sensors. Results evidence that the Er3+ doped LiYbW2O8 phosphors can be outstanding candidates for optical temperature sensors with high Sr and Sa.

Nb-doping in LiNi0.8Co0.1Mn0.1O2 cathode material: Effect on the cycling stability and voltage decay at high rates

Abstract Layered structure nickel-rich LiNi0.8Co0.1Mn0.1O2 possesses the superiority of high discharge capacity and voltage platform. However, the cycling instability and seriously voltage decay limited its cosmically commercial. Herein, Nb-doped Li(Ni0.8Co0.1Mn0.1)O2 cathode materials are synthesized by urea hydrothermal method assisted high temperature solid state process aimed at improving the cycle stability and inhibiting the voltage decay. The analysis results show that the Nb-doped samples reveal a silkworm shape with loosely aggregated surface, stable structure and enlarged diffusion coefficient of Li-ion. The electrochemical data indicates that Nb-doping not only enhance the rate and cycle performance at a high cut-off voltage of 4.6 V, but also inhibit the voltage decay at high rates. Between 2.8 V and 4.6 V, after 100 cycles, the capacity retention of 1% Nb-doped sample is 10.7% and 17% higher than that of the pristine sample at 1 C and 5 C, respectively.

Photoluminescence characteristics of Sm3+-doped LnBWO6 (Ln = La, Gd and Y) as new orange-red phosphors

A series of Sm3+-doped LnBWO6 (Ln = La, Gd and Y) phosphors with orange-red light emitting in pure phase were prepared by high temperature solid-state process. The crystal structure, photoluminescence properties, decay lifetimes and thermal stability properties of those as-prepared samples were investigated. Those phosphors can be efficiently excited by near-UV and blue light and emitted orange-red luminescence with color coordinates (0.622, 0.377). Among those LnBWO6 (Ln = La, Gd and Y) hosts, the emission intensities of Sm3+-doped LaBWO6 are the strongest ones. The optimum doping concentration and critical energy transfer distance of Sm3+ ions in LaBWO6 were determined. The fluorescence concentration quenching mechanism was attributed to the dipole-dipole interaction between the Sm3+ ions. The fluorescent thermal quenching studies showed Sm3+ doped LaBWO6 had high thermal-stable properties. The present work suggested that Sm3+-doped LnBWO6 (Ln = La, Gd and Y) as orange-red phosphors exhibited potential application in white LED.

Study on Potassium Doped Modification of Li1.2Ni0.13Co0.13Mn0.54O2 Materials Synthesized by Novel Method for Lithium Ion Battery

Lithium-rich ternary cathode material Li1.2Ni0.13Co0.13Mn0.54O2 and K+–doped Li1.2Ni0.13Co0.13Mn0.54O2 materials have been successfully prepared via co–precipitation method, followed by a high-temperature solid state process. The chemical component, crystal structure and morphology, surface valence states are conducted by ICP, XRD refinement, FESEM and XPS analysis. Electrochemical properties and Li+ diffusion behavior have been extensively studied. The Rietveld refinement results reveal that the c/a ratio increases induced by K+ doping. Electrochemical studies indicate that the reasonable amount of K+–doped material exhibits the better cycling stability and rate performance. The study indicates that K+ doping hinders the lithium ions migration, thus excesses of K+ doping leads to the cycling stability and rate performance degradation.

Recycling Y and Eu from Waste Fluorescent Powder and High Temperature Solid-State Synthesis of Y2O3:Eu Phosphors

Y2O3:Eu were prepared through precursors synthesized by leaching tests, removing impurities, enrichment of Y and Eu from residual purified liquors, annealing treatment, and high temperature solid-state reaction method, which is the most suitable for large-scale production. The analysis of product shows that the purity is 99.42%. The resultant powders were characterized by X-ray diffraction (XRD), differential thermal analysis (TG-DTA), scanning electron microscope (SEM), and photoluminescence (PL). Compared with the commercial phosphors, the XRD spectrum of the product samples revealed the synthesized particles to have a pure cubic Y2O3:Eu structure without any impurities in the crystalline phase. On the morphology, the Y2O3:Eu particles synthesized by a combustion and high temperature solid state process with sintering aids, were large and uniform. For luminescence property, the emission intensity of Y2O3:Eu phosphors synthesized by combustion process and high temperature solid state process with sintering aids were higher than those without sintering aids, at 1400 °C.

Preparation of Cordierite–Mullite Composite Crucibles and Structure Characterization

Cordierite–mullite composite crucibles were prepared via high-temperature solid-state process by using burn talc, datong soil, knar clay, bentonite, quartz, feldspar and alumina as raw materials, waste porcelain powder as skeletal material. The main influencing factors such as the raw materials radio and calcination temperature were discussed. The microstructure of the sintered sample was analyzed with X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The results show that the optimal prescription was sample II (13.34 wt% of burn talc, 10.496wt% datong soil, 40.65% knar clay, 15.00wt% waste porcelain powder,10.34wt% bentonite, 2.17wt% feldspar, 1.61wt% quartz, and 6.394wt% of alumina). The optimal sintered temperature was 1380°C and the holding time was 3 hours.

Enhanced Hydrogen Production over C-Doped CdO Photocatalyst in NaS/NaSO Solution under Visible Light Irradiation

The C-doped CdO photocatalysts were simply prepared by high-temperature solid-state process. The as-prepared photocatalysts were characterized by X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the carbon was doped into CdO, resulting in the red-shift of the optical absorption of CdO. The photocatalytic behavior of CdO and C-doped CdO was evaluated under the visible light irradiation by using the photocatalytic hydrogen evolution as a model reaction. The C-doped CdO photocatalysts had higher photocatalytic activity over parent CdO under visible light irradiation. The results indicated that the H2production was due to the existence of CdS and the enhancement of visible light photocatalytic activity of H2production was originated from the doping of carbon into the CdO lattice. The probably reaction mechanism was also discussed and proposed.