NaBr-Assisted Sintering of Na3Zr2Si2PO12 Ceramic Electrolyte Stabilizes a Rechargeable Solid-state Sodium Metal Battery.

Solid-state metal batteries with nonflammable solid-state electrolytes are regarded as the next generation of energy storage technology on account of their high safety and energy density. However, as for most solid electrolytes, low room temperature ionic conductivity and interfacial issues hinder their practical application. In this work, Na super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) electrolytes with improved ionic conductivity are synthesized by the NaBr-assisted sintering method. The effects of the NaBr sintering aid on the crystalline phase, microstructure, densification degree, and electrical performance as well as the electrochemical performances of the NZSP ceramic electrolyte are investigated in detail. Specifically, the NZSP-7%NaBr-1150 ceramic electrolyte has an ionic conductivity of 1.2 × 10-3 S cm-1 (at 25 °C) together with an activation energy of 0.28 eV. A low interfacial resistance of 35 Ω cm2 is achieved with the Na/NZSP-7%NaBr-1150 interface. Furthermore, the Na/NZSP-7%NaBr-1150/Na3V2(PO4)3 battery manifests excellent cycling stability with a capacity retention of 98% after 400 cycles at 1 C and 25 °C.

Mn4+-Activated Double-Perovskite-Type Sr2LuNbO6 Multifunctional Phosphor for Optical Probing and Lighting.

Multifunctional phosphors have significant application and scientific value and are becoming a research hotspot in the field of luminescent materials. Herein, we report Mn4+-activated double-perovskite-type Sr2LuNbO6 multifunctional phosphors with excellent comprehensive properties in the fields of optical temperature/pressure sensing and w-LED lighting. The crystalline structure, elemental composition, optimal doping concentration, crystal-field strength, and optical bandgap of the phosphors are investigated in detail, and the mechanisms of concentration and thermal quenching are discussed. From the optimal Sr2LuNb0.998O6:0.2%Mn4+ phosphor, a LED lamp for indoor warm-white lighting is successfully fabricated. Further, the thermometric properties of the phosphors are explored for applications as FIR- and lifetime-based thermometers, showing a maximum relative sensitivity of 1.55% K-1 at 519 K. Upon pressure loading, a significant red-shift of the peak centroid is observed, and the pressure sensitivity is determined to be 0.82 nm/GPa. These results suggest that the Mn4+-activated Sr2LuNbO6 multifunctional phosphors have great potential to be utilized in the fields of optical thermometry, manometry, and lighting.

Dual-Function of Cation-Doping to Activate Cationic and Anionic Redox in a Mn-Based Sodium-Layered Oxide Cathode.

Recently, sodium-ion batteries have shown great potential for energy storage owing to their favorable electrochemical properties and intrinsic cost performance, which fuels the research and development of Mn-based layered oxides as promising sodium-ion cathodes. However, the undesirable structural evolution and oxygen redox impose great challenge on the cycling stability and rate capability of such cathodes. In this work, it is reported that Fe and Al can effectively tailor the Na2/3 Mn2/3 Fe1/6 Al1/6 O2 to trigger a stable cationic and anionic redox behavior. In situ X-ray diffraction analysis confirms the retention of a stable P2 phase upon cycling, and density functional theory results demonstrate that Al3+ doping can strengthen the covalency of MnO bond. The Na2/3 Mn2/3 Fe1/6 Al1/6 O2 cathode can retain 90% of its initial capacity within the voltage range of 2.0-4.2 V versus Na+ /Na at 200 mA g-1 after 100 cycles. Moreover, ex situ X-ray photoelectron spectroscopy reveals that the specific capacity can be replenished by the synergistic reactions between Fe3+ /Fe4+ /Fe3+ and O2- /(O2 )n - pairs within the voltage range of 4.0-4.4 V versus Na+ /Na, which is also elucidated by theoretical calculation.

Fabrication and optical properties of Pr3+-doped Ba (Sn, Zr, Mg, Ta) O3 transparent ceramic phosphor.

To the best of our knowledge, we have successfully fabricated a novel transparent ceramic phosphor of Pr3+-doped Ba (Sn, Zr, Mg, Ta) O3 (Pr3+:BMT) via a high-temperature solid-state reaction method. The in-line transmittance of 59% at 650 nm was measured. The Pr3+:BMT ceramic phosphor can emit 650 nm red light excited by 447 nm blue light. The ceramic phosphor can still work at 383 K. The activation energy was calculated to be 0.17 eV. The efficiency of the ceramic phosphor is twice that of its powder phosphor. The Pr3+:BMT ceramic phosphor showed good thermal stability and enhanced the chromaticity of its white LEDs, which make it a promising red phosphor for lighting.

Strongly enhanced luminescence of Sr4Al14O25:Mn4+ phosphor by co-doping B3+ and Na+ ions with red emission for plant growth LEDs.

Development of a more cost-effective radiation source for use in plant-growing facilities would be of significant benefit for commercial crop production applications. A series of co-doped B3+ and Na+ ions Sr4Al14O25:Mn4+ inorganic luminescence materials which can be used for plant growth were successfully synthesized through a conventional high-temperature solid-state reaction. Powder X-ray diffraction was used to confirm the crystal structure and phase purity of the obtained samples. Then scanning electron microscopy elemental mapping was undertaken to characterize the distribution of the doped ions. Detail investigations on the photoluminescence emission and excitation spectra revealed that emission intensity of tetravalent manganese ions can be well enhanced by monovalent sodium ions and trivalent boron ions under near-ultraviolet and blue excitation. Additionally, crystal field parameters and energies of states are calculated and discussed in detail. Particularly we achieve a photoluminescence internal quantum yield as high as 60.8% under 450 nm blue light excitation for Sr4Al14O25:Mn4+, Na+, B3+. Therefore, satisfactory luminescence properties make these phosphors available to LEDs for plant growth.

M8MgSc(PO4)7:xDy3+ (M = Ca/Sr) Single-Phase Full-Color Phosphor with High Thermal Emission Stability.

Two series of phosphors of Ca8MgSc(PO4)7:Dy3+ and Sr8MgSc(PO4)7:Dy3+ single-phase white-emitting phosphors with high thermal emission stability are synthesized by the high-temperature solid-state reaction. The crystal structure, photoluminescence (PL), PL excitation (PLE), and thermal PL quenching spectra of Ca8MgSc(PO4)7:xDy3+ and Sr8MgSc(PO4)7:xDy3+ were investigated and compared in detail. Upon excitation at 387 nm, M8MgSc(PO4)7:xDy3+ (M = Ca/Sr) showed white emission centered at 480, 571, 660, and 754 nm. The white-emitting Dy-phosphor Ca8MgSc(PO4)7:Dy3+ (CMSP:Dy) had good terminal stability. The emission intensity of Ca8MgSc(PO4)7:Dy3+ still remained 95.2% of that at room temperature at 160 °C, and remained 77.3% at 300 °C under 387 nm excitation.

Enhanced Luminescence Performances of Tunable Lu3-xYxAl5O12:Mn4+ Red Phosphor by Ions of Rn+ (Li+, Na+, Ca2+, Mg2+, Sr2+, Sc3+).

A novel red-emitting Lu3Al5O12:Mn4+ (LuAG:Mn4+) phosphor was synthesized by a solid-state reaction. The emission-band position is shifted to red region by gradually increasing the amount of substitution of Lu3+ for Y3+, eventually yielding fully Y3Al5O12:Mn4+ (YAG:Mn4+). The compared structural and optical properties of the phosphors were investigated. From the experimentally measured spectroscopic data, crystal field parameter Dq and Racah parameters B and C are calculated to be 2127, 1464, and 3620 cm-1 in LuAG:Mn4+, respectively. In YAG:Mn4+, Dq, B, and C are calculated to be 2082, 1524, and 3740 cm-1, respectively. Impressively, Ca2+/Li+/Mg2+/Sr2+/Sc3+/Na+ dopants were found to be beneficial for enhancing Mn4+ luminescence, and the related mechanisms were systematically discussed.

Longitudinally diode-pumped planar waveguide YAG/Yb:LuAG/YAG ceramic laser at 1030.7 nm.

Composite YAG/15 at. % Yb:LuAG/YAG transparent ceramic planar waveguide was fabricated by a tape casting method and vacuum sintering technology. Under a 970 nm diode laser pumping, the absorbed efficiency of 85.4% was achieved, and efficient CW laser operation at 1030.7 nm was accomplished with a good beam quality with Gaussian spatial profile. A maximum output power of 288 mW was obtained under a pump power of 4.69 W, corresponding to a slope efficiency of 9% and an O-O conversion efficiency of 5%.

Introduction on the fabrication technique of phosphor in glass by tape-casting and investigation on the chromaticity property.

We introduce a new fabrication technique of phosphor in glass (PiG) for light-emitting diodes (LEDs) employing the tape-casting. Through the detailed process described herein and the measurement results, it is clear that the PiG-on-glass not only share the same characteristic of those obtained from other techniques or the bulk PiG, but with more precisely controlled width from a few to hundreds micrometers. The samples are mounted on blue InGaN LED chips to test the color properties of the white light. Besides, we established an empirical model that could predict the final color properties of LEDs solely by the phosphor concentration of phosphor glass under certain conditions. This model would greatly facilitate the design of PiG-based LEDs.