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A stable and scalable polymer‐stabilized liquid crystal window which electrically switches from transparent to opaque has been fabricated. Scanning electron microscope measurement shows that higher polymer concentration will induce denser polymer network in polymer stabilized liquid crystal system and then stronger anchoring force between polymer network and liquid crystal molecules, which resulting in larger operating voltage. The cell with larger cell gap has a lower saturated transmittance in the voltage‐on state, which attributed to a larger number of scattering domains in thick cell. The optimized cell exhibits a highly transparent voltage‐off state (3.5% haze) and a voltage‐on scattering state (98% haze) with the threshold voltage of around 20 V. The durability test shows that the optical device switches at least 100,000 times without degradation of optical contrast and shows a high temperature tolerance. Meanwhile, a 40 × 50 cm2 window has been developed in an industrial production line showing the same optical properties. Our results demonstrate the fabrication of smart windows with a highly transparent rest state and high optical contrast on a commercial mass production scale, making them attractive for applications in buildings, automobiles, and switchable sunglasses for light management and potentially energy saving. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48917. [ABSTRACT FROM AUTHOR]

The luminescence properties of Eu 2+ in AgCa 10 (PO 4 ) 7 has been studied at room and low temperature and the decay times of Eu 2+ in this matrix have been measured and analyzed. According to the crystal structure of AgCa 10 (PO 4 ) 7 , photoluminescence (PL) spectra and decay curves, the substitution of Eu 2+ ions is possible to four different Ca 2+ sites. The red-shift of emission wavelength and energy transfer process between Eu 2+ activator ions are discussed. [ABSTRACT FROM AUTHOR]

The optical properties of LiBaBO3 doped with Eu2+ are investigated in the temperature regime between 10 and 525 K for the first time. At room temperature (RT), a broad emission band peaking around 485 nm is observed. The emission is ascribed to the 4f65d1 → 4f7 transition on Eu2+. The excitation spectra consist of broad bands between 220 and 450 nm. The emission intensity shows no remarkable decline at lower temperatures; although it decreases drastically at higher temperatures. The Stokes shift is calculated to be 0.52 eV. The thermal activation of an electron from the Eu2+ excited state to the conduction band is responsible for the thermal quenching behavior in LiBaBO3:Eu system. The energy gap EA for the best fit of decay time is 0.38 eV. [ABSTRACT FROM AUTHOR]

A series of Ce 3+ doped Ca 3 B 2 O 6 phosphors with different doping concentration were prepared by using a high-temperature solid-state reaction technique. The luminescence properties under UV excitation were studied. From the photoluminescence (PL) excitation and emission spectra we conclude that two Ce 3+ sites (Ce I and Ce II) exist in host crystal. The tunable emission properties of Ce 3+ -doped Ca 3 B 2 O 6 phosphors are analyzed by using Ce 3+ ions occupancy probability between Ce I and Ce II and possible energy transfer between Ce I and Ce II center. [ABSTRACT FROM AUTHOR]

This article reports on the optical properties of Sm3+-activated GdB3O6phosphors based on the measurement of their photoluminescence spectra and luminescence decay curves. Energy transfer from Gd3+to Sm3+and the concentration quenching of the Sm3+ion emission are investigated. From the photoluminescence spectra and decay curves, the energy transfer from Gd3+to Sm3+is confirmed. The concentration quenching of the Sm3+ion emission can be ascribed to resonant cross-relaxation. The interaction between the Sm3+ions is derived of the electric dipole–dipole type through fitting the data with the Inokuti-Hirayama model. The critical distances and energy transfer microparameter for the transfer processes are given. The decay curves of Sm3+4G5/2level exhibiting a buildup and decay process also confirm the energy transfer from Gd3+to Sm3+and between Sm3+ions. [ABSTRACT FROM PUBLISHER]

Highlights: [•] SrLiB9O15:Ce3+/Tb3+ phosphors were studied for the first time. [•] Ce3+ ions occupy two different sites (Ce I and Ce II) in SrLiB9O15 crystal. [•] Ce3+ ions substitute Sr2+ sites and interstitial sites simultaneously. [•] Energy transfer behavior from Ce3+ to Tb3+ is confirmed. [•] The energy transfer occurs from Ce II to Tb3+ in this case. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lifetime of Gd decreases with Dy concentration, confirming energy transfer. [•] Rise time confirms the feeding of the Dy excited state by energy transfer. [•] Concentration quenching of Dy emission is ascribed to resonant cross-relaxation. [•] Interaction between Dy ions is dipole-dipole type through fitting with I-H model. [ABSTRACT FROM AUTHOR]

Abstract: Sr2Mg(BO3)2:Ce3+,Li+ and Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors have been synthesized by conventional solid state reaction technology at 900°C for 12h in reducing atmosphere. The phase purity, photoluminescence (PL) properties, thermal stability, energy transfer and luminescent decay curves have been investigated. Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ phosphors show blue and deep-red [1] For interpretation of color in Figs. 1–6, the reader is referred to the web version of this article. 1 emission bands. The deep-red emission band is attributed to the energy transfer from Ce3+ to Mn2+. The fluorescence lifetimes of Ce3+ in co-doped sample are shorter than that in single doped one, which confirms that the energy transfer takes place. The phosphors have weak thermal quenching. The luminescence properties of Sr2Mg(BO3)2:Ce3+,Li+,Mn2+ make the phosphor a new bicolor emitting material. [Copyright &y& Elsevier]

The luminescence properties and site occupation of NaScP 2 O 7 :Ce 3+ and KScP 2 O 7 :Ce 3+ phosphors are reported for the first time. Two principal Ce 3+ sites [Ce (I) and Ce (II)] are observed. One of the Ce 3+ centers is found to be produced by the direct substitution of the dopant ion for Na + /K + without a local charge compensation. Another center is ascribed to an associate of a Ce 3+ ion and a cation vacancy. The zero-phonon line E 0 and Stokes shift are calculated. [ABSTRACT FROM AUTHOR]

Abstract: Orange-emitting Sr3Al2O5Cl2:Eu2+ phosphors were synthesized by a high-temperature solid-state reaction. The excitation spectrum shows a broad band from the UV region to the blue region. The emission spectrum shows strong orange emission peaking at 610 nm, attributed to the d–f transition of the Eu2+ ion. By combining the Sr3Al2O5Cl2:Eu2+ phosphor with 420 nm and 460 nm chips, three white light-emitting diodes (LEDs) were fabricated. The warm-white LEDs show color rendering indexes of 76, 66 and 90 with color temperatures of 2447, 3546 and 4300 K, respectively. This new phosphor exhibits the potential to act as a single host doped with Eu2+ phosphor for UV or blue chip excited white LEDs. [Copyright &y& Elsevier]

Abstract: Mn2+-doped Ba2ZnS3 phosphors for white light emitting diodes (LEDs) have been prepared by high temperature solid-state reaction and their photoluminescence properties are reported. Diffuse reflection spectra of Ba2ZnS3 host and synthesized phosphors have been measured. The excitation spectrum extends a broad range of wavelength and is consistent with the diffuse reflectance spectra. The emission bands are due to 4T1(4G)→ 6A1(6S) transition of the Mn2+ ion and there exists efficient energy transfer from host to Mn2+ ions. The dependence of emission wavelength on Mn2+ concentration is studied. The decay curve of Mn2+ ions luminescence in Ba2Zn0.995S3:0.005 Mn2+ is also measured. [Copyright &y& Elsevier]

Charge compensating defects, resulting from heterovalent cation substitution, often play an important role in luminescent properties. In this paper, the luminescence properties of K 2 MgSi 3 O 8 :Eu2+ phosphor were studied by means of XRD, PL and decay analysis. It is found that there was only one K+ site to be substituted by Eu2+ in the K 2 MgSi 3 O 8 host lattice. However, the existence of multiple Eu2+ sites is observed, which is explained by charge compensating mechanism. Unequal substitution is a meaningful way to discover new luminescent materials. [ABSTRACT FROM AUTHOR]

Abstract: Novel Eu3+-doped NaCa4(BO3)3 phosphors were synthesized by solid-state reactions. The emission spectra exhibit well-known transitions from the 5D0 level to the lower 7F manifold. The excitation spectrum monitored with 613nm consists of broad excitation band peaking at 265nm and some narrow lines originated from the typical Eu3+ intra-4f6 transitions. The optimum Eu3+ doped concentration, the critical distance of the concentration quenching, the fluorescence decay curves, and the mechanism of concentration quenching are investigated. [Copyright &y& Elsevier]

Investigation on Ce3+ ions occupying different cation sites of a specific compound is of great significance for exploring multicolor phosphors. Herein, we report the luminescent properties of Ce3+ in chloroborate Ca 2 BO 3 Cl host. Two kinds of Ce3+ f - d transitions have been observed via adjusting the doping concentration. The assignment for different Ce3+ sites to certain cation sites is corroborated by structural analysis (XRD), fluorescence spectroscopy (PL) and decay kinetic analysis. Information on the two Ce3+ sites' wavelengths of the five 5 d bands in the Ca 2 BO 3 Cl host lattice together with ε cfs , ɛ c , D and Δ S are obtained. Moreover, with the increasing of Ce3+ doping concentration, the emission peak shows an obviously redshift, and the emission color changes from dark blue to blue. The tuning luminescence properties are attributed to the energy transfer from Ce II to Ce I. The optical properties of the as-fabricated white light-emitting diode (LED) are studied. However, the optical properties of current studied Ce3+ doped Ca 2 BO 3 Cl is not good enough to be a candidate for near-UV chip excited phosphor-converted white LED. • Ce I and Ce II sites are confirmed by fluorescence spectroscopy and decay kinetic. • The mechanism of emission spectra red-shift is discussed. • 5d bands of Ce3+ sites in Ca 2 BO 3 Cl together with ε cfs , ɛ c , D and Δ S are obtained. • Ca 2 BO 3 Cl:Ce3+, Na+ is a potential blue phosphor for near-UV excited white LEDs. [ABSTRACT FROM AUTHOR]

New potassium gadolinium phosphate [K 3 Gd 5 (PO 4 ) 6 ] doped with Eu 3+ , Ce 3+ , Tb 3+ and co-doped with Ce 3+ and Tb 3+ phosphors were prepared by high temperature solid state synthesis. Phase purity of the powders was checked by X-ray powder diffraction. Luminescence and excitation spectra of samples were reported. In particular, the interaction mechanism between Eu 3+ ions was investigated in terms of the Inokuti–Hirayama model; it was found that the interactions between Eu 3+ can be assigned to dipole–dipole interaction. K 3 Gd 5 (PO 4 ) 6 :Eu 3+ could act as a candidate for solid state lighting due to its strong absorption band in the near-UV region (350–400 nm). The energy transfer from Ce 3+ to Tb 3+ was confirmed and the mechanism was studied using Dexter's theory; it is concluded that electric dipole–dipole interaction predominates in the energy transfer process from Ce 3+ to Tb 3+ in the K 3 Gd 5 (PO 4 ) 6 host. The energy transfer efficiency and critical distance were also investigated. [ABSTRACT FROM AUTHOR]