Search

Abstract To fabricate white-light-emitting diodes (white LEDs) with high color-rendering index or full light spectrum emission, the discovery of more efficient deep-red emitting phosphor materials is essential. In this paper, we have synthesized a series of Sr 2-2x Eu 2x Si 5 N 8 (0 ≤ x ≤ 1) solid-solution compounds, and have systemically investigated effects of full-range Eu concentration on their luminescence. Their emission band maximum can be largely tuned from 610 to 725 nm by increasing Eu content. Reabsorption at low Eu2+ concentration while both the energy transfer and Stocks shift at high Eu2+ concentration account for this large spectral red-shift. Luminescent thermal quenching performance gets worse with Eu2+ concentration increasing. The compound with x = 0.15 possesses the best crystallinity and the highest luminescence intensity with the peak position around 660 nm, and still maintains 88.5% room-temperature intensity at 400 K, indicating that great potential for the application as a deep-red phosphor. Highlights • A full-range Sr 2-2x Eu 2x Si 5 N 8 (0 ≤ x ≤ 1) solid solution was synthesized. • Largely tunable red emission band from 610 to 725 nm by adjusting Eu content. • High quenching concentration and high thermal quenching temperature for Eu2+ emission. [ABSTRACT FROM AUTHOR]

The red persistent luminescence of CaTiO 3 :Pr 3+ needs further improvement in longer excitation wavelength to fulfill the application demand. By Na + -Nb 5+ substituting for Ca 2+ -Ti 4+ , a series of Pr 3+ -doped perovskite-type (Ca 1- x Na x ) [Ti 1- x Nb x ]O 3 :0.001Pr 3+ compounds, with a structural transition at about x = 0.7–0.8, have been successfully synthesized by a solid state reaction. The excitation band first red-shift and then blue-shift gradually with x . The afterglow duration has been prolonged from 30 s for CaTiO 3 :Pr 3+ to about 60 s for the composition x = 0.1. Wavelength-dependent trap filling analysis show that the charging wavelengths can be red-shifted from UV irradiation (<358 nm) for CaTiO 3 :Pr 3+ to visible violet light for compositions with x = 0.1. On the basis of spectral data, we construct the host referred binding energy (HRBE) and vacuum referred binding energy (VRBE) schemes of trivalent lanthanide-doped (Ca 1- x Na x ) [Ti 1- x Nb x ] O 3 compounds, and further explain these afterglow behaviors. This work is helpful for exploring novel persistent luminescent materials. [ABSTRACT FROM AUTHOR]

LiMn 0.8 Fe 0.2 PO 4 nanocrystal composite cathode material for lithium ion batteries was prepared via a simple solvothermal method. The quinoline soluble substance from coal pitch (QS) was used as the coated carbon source to prepare LiMn 0.8 Fe 0.2 PO 4 /C. The structural performance of QS and QS-C, and the effects of QS-C on the physical, chemical and electrochemical properties of LiMn 0.8 Fe 0.2 PO 4 /C were investigated. The research shows that QS is an aromatic compound containing C–N and C–S bonds, and the structure of QS-C is a streamlined structure with high graphitization degree. Hence, the N, S-dual doped carbon conductive network can be effectively established to enhance charge transfer and the diffusion and migration rate of lithium ion. The prepared LiMn 0.8 Fe 0.2 PO 4 /C delivery excellent specific discharge capacity of 159.2, 145.7, and 117.3 mAh·g-1 at 0.1, 1, and 5 C, respectively. After 150 cycles at 1 C, the specific discharge capacity was still 133.5 mAh·g-1, and the capacity retention is 93%. This work provides a new insight into the search for coated carbon sources. • High-performance LiMn 0.8 Fe 0.2 PO 4 /C is constructed by using quinoline soluble substance from coal pitch (QS) as carbon source. • QS contains C-S and C-N bonds, and its pyrolysis carbon has a streamlined structure with a high degree of graphitization. • Nitrogen and sulfur co-doped carbon conductive network can be successfully prepared. • The capacity of QS-6.4–670 is 159.2 and 145.7 mAh·g-1 at 0.1 and 1 C, showing the retention of 93% after 150 cycles at 1 C. [ABSTRACT FROM AUTHOR]

A metallic closed cellular material containing organic materials for damping systems has been developed. Powder particles of polystyrene coated with a nickel–phosphorus alloy layer using electroless plating were pressed into green pellets and sintered at high temperatures in a vacuum. A metallic closed cellular material containing organic materials was then fabricated. The density of this material is lower than that of other structural metals. Compressive tests and ultrasonic measurements were carried out to measure the mechanical and ultrasonic properties of this material, respectively. The results showed that this material had different stress–strain curves among the specimens that had different cell wall thicknesses, each stress–strain curve had a long plateau region, the sintering temperatures of the specimens affect the compressive strength of each specimen, and energy absorbing capacity is very high. The internal friction of this material measured by the half width method is very high. These results indicate that this metallic closed cellular material can be utilized as an energy absorbing material and passive damping material. [Copyright &y& Elsevier]

Stable and high-efficiency narrow-band green phosphor is a key component for wide color gamut liquid crystal display (LCD) backlights. In this paper, narrow-band green-emitting Sr 3-3x Si 13 Al 3 O 2 N 21 :3xEu2+ (0.001 ≤ x ≤ 0.09) (Sr-Sialon:Eu2+) phosphor with a full-width at half maximum of 66 nm has been successfully synthesized by using the solid-state reaction method. All the samples are the pure phase with Sr 3 Si 13 Al 3 O 2 N 21 -type structure. Their emission band maximum can be tuned from 495 to 523 nm by increasing Eu2+ content. The compound with x = 0.03 possesses the highest luminescence intensity with the peak position around 510 nm. Luminescent thermal stability gets better with Eu2+ concentration decreasing. The integrated intensity of the sample with x = 0.01 at 425 K remains about 80% of the intensity at room temperature. The host referred binding energy (HRBE) and vacuum referred binding energy (VRBE) schemes are constructed to further explain its luminescent thermal quenching mechanism. White light-emitting-diode (w -LED) device using optimized Sr 2.91 Si 13 Al 3 O 2 N 21 :0.09Eu2+ phosphor demonstrates its potential application for LCD backlights. • The emission peaks of Sr 3-3x Si 13 Al 3 O 2 N 21 :3xEu2+ can be tuned from 495 to 523 nm by increasing Eu2+ content. • Luminescent thermal stability gets better with Eu2+ concentration decreasing. • HRBE and VRBE schemes for Sr-Sialon:Eu2+ phosphor are constructed. [ABSTRACT FROM AUTHOR]

Garnet-type electrolyte have received a lot of attention due to its high ionic conductivity, wide electrochemical window, excellent thermal stability and lithium metal stability, which can match high-voltage cathode and lithium metal anode to promote the safety and energy density of the batteries. The preparation of solid electrolytes frequently necessitates high-temperature solid-state reaction method. However, this method would cause volatile lithium compounds, restricting the practical preparation and application of electrolytes. Herein, the impact of Li 2 CuO 2 (LCO) as a sintering additive on the sintering behavior of Ta-doped garnet-type electrolyte (Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 , LLZT) is investigated. LCO plays an auxiliary sintering role to reduce the sintering temperature, and the internal Li 2 O atmosphere that is provided by LCO helps densification of LLZT. The relative density of LLZT-0.5 LCO is 96.07 %, and its Li-ion conductivity is 3.6 × 10−4 S cm−1. Li symmetric and full batteries show excellent cycling performance. This facile and effective strategy of utilizing sintering additive for low temperature sintering could offer useful ideas for the low-cost fabrication of LLZT. [Display omitted] • Studied effect of Li 2 CuO 2 (LCO) on morphology and electrochemistry of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT). • LCO as a novel sintering additive can efficiently lower the sintering temperature of LLZT. • Enhanced Li dendrite-suppression ability benefits from strong grain-to-grain bonding. • Full batteries exhibit excellent cycling stability. [ABSTRACT FROM AUTHOR]

• Highly efficient Ca 3 Y 2 Ge 3 O 12 :Cr3+ phosphors have been synthesized. • The excitation wavelength matches the blue LED chip. • The abroad emission peaked at 800 nm due to Cr3+ in six-coordinated Y3+ site. Near-infrared phosphor (NIR) integrated light-emitting diode (LED) has ideal application prospects in the fields of food inspection and medical imaging. Herein, we have synthesized a garnet-type Ca 3 Y 2 Ge 3 O 12 :Cr3+ NIR phosphor using solid state reaction method. Broadband NIR emission ranging from 700 to 1100 nm with a peak located at 800 nm indicates a weak crystal field strength for Cr3+, which occupies the six-coordinated Y3+ site. Moreover, the phosphor has satisfactory luminous intensity showing 81%/10% internal/external quantum efficiency and excellent luminescence thermal stability. Our work provides an excellent NIR phosphor choice for NIR LED devices. [ABSTRACT FROM AUTHOR]

Li-garnet Li 7 La 3 Zr 2 O 12 (LLZO) is a promising solid electrolyte for lithium metal batteries owing to its excellent stability and high ionic conductivity. However, there exists serious lithium dendrite problem in LLZO electrolyte under elevated current density, easily leading to internal short-circuit and poor cycling performance. In this work, we demonstrated that Ta-doped LLZO with 4 wt% MgO additive delivered superior endurance to lithium dendrite due to its improved mechanical properties and lower electronic conductivity. The critical current density (CCD) of LLZTO-MgO composite electrolyte reached as high as 1.95 mA⸳cm−2 at room temperature (RT). It also realized stable lithium plating/stripping performance for 1000h under 0.5 mA⸳cm−2. Moreover, the full cell paired with LiNi 0·6 Co 0·2 Mn 0·2 O 2 cathode exhibited better cycling stability especially at a high rate. Our work provided an alternative strategy for dendrite-suppression in solid electrolyte besides interfacial modification. • An effective measure for dendrite problem via mechanically preparing LLZTO-MgO composite electrolytes. • The mechanism of MgO is proposed from: mechanical property & electronic conduction. • The arguments from three parts: critical current density; long-cycling stability; cycling lifespan at high rates. [ABSTRACT FROM AUTHOR]

Ca-α-Sialon: Eu2+, a well-known yellow phosphor, has been widely studied due to its broad UV-blue excitation with high quantum efficiency. Herein, we report the yellow persistent luminescence (PersL) of a series of Ca-α-Sialon: Eu2+ compounds with chemical formula CaSi 10-n Al 2+n O n N 16-n : x Eu2+ (m = 2, n = 0∼1, x = 0.1%∼8%) prepared by high-temperature solid-state method. Upon 254 nm ultraviolet excitation, Ca-α-Sialon: Eu2+ shows yellow PersL, and the persistent time is strongly dependent on the Eu2+ and oxygen concentrations. The best persistent time is measured to be about 60 min for the CaSi 10 Al 2 N 16 : 0.5% Eu2+ sample. A very broad trap depth distribution, i.e. 0.6–1.4 eV, originating from two categories, are obtained by analyzing preheating thermoluminescence (TL) spectra using initial rise method. Comparing thermoluminescence excitation spectra (TLEs) with photoluminescence excitation spectra (PLEs), we verify that electrons as charge carriers are excited from 4 f ground state of Eu2+ to conduction band (CB) directly in the charging process for PersL. By functional theory (DFT) calculations, we verify that the trap levels responsible for PersL are impurity defects including V O and V N in Ca-α-Sialon. Furthermore, the PersL mechanism is given on the basis of constructing the host referred binding energy (HRBE) diagram. By virtue of NIR photo-stimulating PersL spectrum, we demonstrate that Ca-α-Sialon has a potential application in anti-counterfeit and information storage. This work would encourage more exploration of Eu2+-doped nitride phosphor for persistent or long-persistent luminescence. • A novel yellow long persistent luminescent Ca-α-Sialon: Eu2+ phosphor is developed. • Trap distribution and roles of traps are studied through experiments and DFT calculation. • The persistent luminescence mechanism of Ca-α-Sialon: Eu2+ phosphor is illustrated using HRBE diagram. [ABSTRACT FROM AUTHOR]