Search

A new chloride borate, Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl, was obtained when exploring potential phosphor materials. It belongs to orthorhombic system, Pnma space group, with cell parameters of a = 6.965(1) Å, b = 16.546(3) Å, c = 9.557(1) Å and Z = 4. Ba 5- x Sr x (BO 3 ) 3 Cl ( x = 0, 0.5, …to 5) was synthesized and the cell volumes of the solid solutions were obtained by Rietveld refinement. Detailed structure description of Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl was conducted and the structure comparison between Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl and M 5 (BO 3 )X (M = Ba or Sr, X = Cl or F) was illustrated. In Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl, there are hexagonal tunnels extending along a -axis, which is the main feature of apatite family compounds. The density functional theory calculation suggested that in Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl space group Pnma is more energy favourable than C 222 1 . DSC-TG showed that Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl is stable up to 950 °C and Raman and Infrared spectroscopy demonstrate the existence of planar (BO 3 ) 3- in the structure. [ABSTRACT FROM AUTHOR]

• Single crystal structure of a novel ultraviolet NLO tourmaline was solved. • Sellmeier equations were obtained by fitting the measured refractive indices. • Phase matching range of the title crystal is obtained from the Sellmeier equations. • The linear and NLO properties were investigated by the experimental and theory calculation. Transparent tourmaline NaAl 9 (BO 3) 3 Si 6 O 21 OH is first reported by combining experimental and theory calculation methods, which exhibits potential ultraviolet nonlinear optical properties. [Display omitted] Tourmaline, as an important mineral, has received intensive interest, since it is not only a valuable gemstone, but also is a piezoelectric or pyroelectric material, due to the polar structural configuration. However, its nonlinear optical (NLO) properties were not explored so far, because a transparent crystal with high transmittance is scarce, being essential to optical functional materials. Here, we report a novel ultraviolet (UV) NLO tourmaline crystal with chemical composition NaAl 9 (BO 3) 3 Si 6 O 21 OH for the first time by combining first-principles analysis and experimental measurements. It exhibits a short UV absorption edge, considerable second harmonic generation effect and moderate birefringence, thereby facilitating its phase-matching coherent beam output in the range from visible to UV regions. [ABSTRACT FROM AUTHOR]

Good thermal stability and high quantum efficiency (QE) are desirable properties for phosphors applied in white light-emitting diodes field. In this work, a Ce3+ doped phosphor Ba 2 LuAl 3 Si 2 O 12 :Ce3+ (BaLuAS:Ce3+) was designed and successfully obtained. Structure analysis of Ba 2 LuAl 3 Si 2 O 12 indicates that it adopts garnet structure and crystallizes in space group I a ¯3 d (No.230) of the cubic system. The wavelength-dependent photoluminescence emission property and the mechanism of concentration quenching effect of BaLuAS:xCe3+ were investigated systematically. The PL emission exhibits high thermal quenching resistance with the quenching temperature (T 50%) reaching up to 673 K (400 °C). By measuring thermoluminescence, the thermal ionization process was discussed. To compensate for the lack of orange-red emission region and avoid using multiple phosphors, Mn2+ ions were introduced into the host. The remarkable enhancements of the orange band are attributed to an efficient nonradiative energy transfer from Ce3+ to Mn2+ ions, which has been testified by the photoluminescence spectra and fluorescence decay dynamics. The w-LED fabrication results suggest that the broad emission of BaLuAS:Ce3+, Mn2+ is suitable for applying in high-quality warm w-LED. Targeted garnet phosphor Ce3+ doped Ba 2 LuAl 3 Si 2 O 12 was achieved via the hetero-valence substitution of Lu3+-Al3+ by Ba2+-Si4+ pairs starting from Lu 3 Al 5 O 12 : Ce3+ and the red component in the emission spectrum has been enhanced through Ce3+-Mn2+ energy transfer. Image 1 • The crystal structure of the compound and the corresponding specific position of Lu/Ba, Al/Si atoms were analysized. • The IQE and EQE of the BaLuASO:0.12Ce3+ phosphor can reach 88.2% and 49.7%, respectively. • The high luminescence quenching temperature (∼673 K) has been well established. • The effective energy transfer from the Ce3+ to Mn2+ ions was justified. [ABSTRACT FROM AUTHOR]

The first two members in the quaternary A/A′/M/Q (A = alkali metal; A′ = alkaline-earth metal; M = As, Sb, Bi; Q = S, Se, Te) system, namely the KBaMSe 3 (M = As, Sb) selenides, have been synthesized by solid state reactions. They are isostructural and crystallize in the centrosymmetric space group P 2 1 / c of the monoclinic system. In the structure, the trivalent M atom (M = As, Sb) is coordinated to three Se atoms forming a trigonal pyramid with the Se atoms serving as the triangle base, showing the stereochemical activity of the ns 2 lone pair electron. The MSe 3 (M = As, Sb) trigonal pyramids are totally isolated from each other with K + and Ba 2+ cations located between them. The optical band gaps of 2.26 (2) eV for KBaAsSe 3 and 2.04 (2) eV for KBaSbSe 3 , were deduced from the diffuse reflectance spectra. The first principles calculations were performed to study the electronic structures of KBaMSe 3 (M = As, Sb) compounds and the results indicated that these two compounds are indirect band gap semiconductors. [ABSTRACT FROM AUTHOR]

A modified gel polymer electrolyte (GPE) with boron nitride (BN) additive was designed to boost the electrochemical performance of rechargeable lithium metal battery, which consists of Li-rich layered cathode and possesses a high energy density. BN, electron insulator and ion conductor, has excellent thermodynamic and electrochemical stability. BN particles were well dispersed in polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) polymer matrices and thus substantially enhanced the electrochemical and physical properties of the GPEs. With only 0.5 wt% BN additive, it remarkably improved the mechanical modulus and ionic conductivity (to 4.1 × 10−4 S∙cm−2) of GPEs, which was beneficial for suppressing lithium dendrite formation and fast ion transportation, respectively, thereby enabling high-performance lithium metal batteries with ultra-long cycle life and high safety at ambient temperature (25 °C) and high temperature (55 °C). A modified GPE with a multifunctional BN additive can revitalize LMBs to readily obtain a comparative ionic conductivity and remarkably improve mechanical modulus, which is beneficial for suppressing Li dendrite formation. Image 1 • We have successfully incorporated 2D BN fillers into a gel polymer electrolyte based on PVDF-HFP. • Only 0.5 wt% addition of BN can readily obtain a comparative ionic conductivity and improved mechanical modulus. • The Li 1.18 Ni 0.15 Co 0.15 Mn 0.52 O 2 /0.5 wt% BN-(PVDF-HFP)/Li cell performs a superior stability and rate capability. [ABSTRACT FROM AUTHOR]

Abstract Self-activated phosphors could convert high energy light into visible light from the internal ion groups of host lattice before externally introducing luminescent ions. In this work, we propose a facile route to synthesize self-activated oxyfluorotungstate (Na 2 WO 2 F 4) phosphor. Excited by the UV light, the emission spectrum covers nearly the entire visible light region. After careful analysis of the first principle calculation results and other sufficient investigation, it is believed that the efficient emission of Na 2 WO 2 F 4 phosphor comes from the strong parity-allowed absorption of O-2 p to W-5d charge transfer band. Moreover, the quantum efficiency of Na 2 WO 2 F 4 phosphor reaches up to 76% at room temperature. However, the increase of temperature not only lowers the intensity of the PL emission and the quantum efficiency but gives rise to a blue shift of the emission maxima, due to the phonon interaction with the luminescence center in a vibrating crystalline environment. Graphical abstract Image 1 Highlights • A self-activated phosphor Na 2 WO 2 F 4 was obtained by a facile route. • The emission spectrum of Na 2 WO 2 F 4 covers nearly the entire visible light region. • The quantum efficiency reaches up to 76% at room temperature. • Thermal quenching and high-energy shift of Na 2 WO 2 F 4 were observed and analyzed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three new chalcohalides: Ba4Ge2PbS8Br2, Ba4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2 have been synthesized. [•] The MQ5Br octahedra and GeQ4 tetrahedra form a three-dimensional framework with Ba2+ in the channels. [•] Band Gaps and electronic structures of the three compounds were studied. [ABSTRACT FROM AUTHOR]