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Coprecipitation with rare‐earth nitrate, ammonium sulfate, and ammonium hydroxide produced hydroxide‐type amorphous precursors incorporating sulfate and carbonate anions, from which [(Gd1−xLax)0.99Tb0.01]2O2SO4 and [(Gd1−xLax)0.99Tb0.01]2O2S (x = 0, 0.15, 0.3, 0.5, 0.65, 0.8, and 1) were obtained as two series of nanophosphors by calcination at 950°C in air and hydrogen, respectively. The detailed characterization by X‐ray diffractometer, scanning electron microscopy/transmission electron microscopy, Brunauer–Emmett–Teller, and particle sizing confirmed that solid solutions were directly formed and that the products have small crystallite size, unimodal size distribution, and high specific surface area, revealing the advantages of the synthesis method. Photoluminescence study revealed that La3+ admixture may significantly improve the 545 nm main emission of Tb3+ for both the phosphor series. Furthermore, the 545 nm main emission of [(Gd1−xLax)0.99Tb0.01]2O2SO4 was identified to have an excellent thermal stability, which retained over 90% of its room‐temperature intensity at 150°C (no quenching for Gd2O2SO4:Tb3+). The two series of phosphors were comparatively studied for their excitation and luminescence performances, as a function of temperature and La3+ content, and the results were rationalized by considering bandgap, crystal structure, UV absorption, and the character of chemical bonds. [ABSTRACT FROM AUTHOR]

Temperature‐sensitive luminescent materials have aroused great interest for practical applications in optical sensors. Layered rare‐earth hydroxides (LRHs) possess rich interlayer chemistry and adjustable composition; thus, they are the promising candidates for designing functional materials, usually through an ion exchange process. Herein, the intercalation of neutral TbIII complex rather than ion exchange was successfully performed in situ into the gallery of Y/Eu binary LRHs by using a hydrothermal process. Interestingly, the swollen LRHs are chameleon luminophores, exhibiting color emissions from green to pink that were tunable through variations in temperature ranging from 77 to 450 K. Because of the highly sensitive and temperature‐dependent emissions, novel optical temperature sensors for 1D and 2D thermal imaging were fabricated by employing the chameleon luminophores, which displayed luminescence capable of reversibly undergoing repeated thermocycles. The present work opens up new fields in layered inorganic materials. Playing to the gallery: The first intercalation of a neutral TbIII complex is successfully performed in situ into the gallery of layered rare‐earth hydroxides (LRH). Novel optical temperature sensors for 1D and 2D thermal imaging are fabricated by employing the allochroic swollen LRHs, which opens up new fields in layered inorganic materials. [ABSTRACT FROM AUTHOR]

Long persistent luminescence materials developed to commercial standards are primarily concentrated in the blue and green regions, with only a few in the red region. Red, as one of the three basic colors, can be mixed in various proportions with blue and green to yield various colors. The development of red persistent phosphors has a broader application potential but remains a challenge. A solid-state reaction method was used to synthesize new red persistent luminescent materials of Ba 1- x Sr x Ga 2 O 4 :Sm3+ (x = 0–0.09). In BaGa 2 O 4 , both Sr2+ and Sm3+ preferentially occupy the Ba2+ site rather than the Ga3+ site. When exposed to UV light at 254 nm, the phosphors emit the characteristic red emission of Sm3+ at wavelengths ranging from 500 nm to 750 nm. After removing the UV light source, an intense red afterglow that lasted more than 1400 s was observed. The red afterglow signal reappears after a heating process. Doping Sr2+ reduces the trap depth and improves the red persistent luminescence significantly. Because the escaped electrons from traps compensate for the emission loss of Sm3+ during the heating process, the red phosphors have unimaginably luminescent thermal stability. Thus, the emission intensity at 200 °C is 1.6 times that at room temperature. The prepared red persistent phosphors show multimode luminescence, with the output signal being time and temperature sensitive, indicating that they are potential luminescent materials for anti-counterfeiting applications. Finally, a building-block strategy for advanced anti-counterfeiting applications of dynamic display information is proposed, with red persistent phosphors serving as an important component combined with upconversion phosphors of NaYF 4 :Yb3+, Tm3+, and green persistent phosphors of SrAl 2 O 4 :Eu2+, Dy3+. [ABSTRACT FROM AUTHOR]

[(Gd 0.8 Lu 0.2 ) 0.9− x Tb 0.1 Eu x ] 3 Al 5 O 12 ( x = 0–0.1) garnet phosphors have been calcined from their coprecipitated carbonate precursors at 1300 °C. Detailed materials characterizations are done via XRD, FE-SEM, BET, particle sizing, PL/PLE, and fluorescence decay analyses. The phosphors, with excellent dispersion and uniform particle size and shape, simultaneously exhibit the characteristic Tb 3+ and Eu 3+ emissions with the strongest peaks located at 545 nm (green) and 592 nm (orange red) under the optimal excitation wavelength of 275 nm, which correspond to the 5 D 4 → 7 F 5 and 5 D 0 → 7 F 1 transitions of Tb 3+ and Eu 3+ , respectively. The emission intensities of both Tb 3+ and Eu 3+ remarkably vary with increasing Eu 3+ incorporation, and, as a consequence, the emission color can be readily tuned from approximately green to orange-red. At the optimal Eu 3+ concentration of x = 0.03, the energy transfer efficiency was calculated to be ∼83.2% and the mechanism of energy transfer was analyzed to be electric dipole–dipole interactions. The processes of energy migration among the optically active Gd 3+ , Tb 3+ , and Eu 3+ ions are discussed in detail. Fluorescence decay analysis found rapidly decreasing lifetime for the Tb 3+ emission, conforming to the Tb 3+ → Eu 3+ energy transfer, and the probability of energy transfer is calculated. The [(Gd 0.8 Lu 0.2 ) 0.9− x Tb 0.1 Eu x ] 3 Al 5 O 12 solid-solutions developed in this work may serve as a new type of phosphor that hopefully meets the requirements of various lighting, optical display, and scintillation applications. [ABSTRACT FROM AUTHOR]

A series of garnet-type Li 6 CaLa 2(1- x) Nb 2 O 12 : x RE phosphors (LCLN: x RE, RE = Pr, Sm, Tb and Dy) were prepared via sol-gel processing and subsequent calcination for the first time, with the course of phase evolution and the characteristics of the LCLN host and RE3+ luminescence being investigated in detail. It was found that ∼900–1000 °C is a suitable temperature for precursor calcination to produce the garnet phase and LCLN has a relatively low phonon energy (∼725 cm−1) and a relatively wide bandgap (∼4.53 eV) for luminescence. The LCLN:0.012Pr, LCLN:0.04Sm, LCLN:0.06 Tb and LCLN:0.06Dy typical phosphors were analyzed to have dominant excitation/emission bands at ∼278/489, 265/614, 268/549 and 264/581 nm, emission colors of white, orange, green and yellowish white, and fluorescence lifetimes of ∼0.43, 0.74, 0.90 and 0.44 ms, respectively. Temperature-dependent photoluminescence found that the four phosphors maintained ∼28, 37, 45 and 56% of their room-temperature intensities at 423 K, with activation energies for thermal quenching of ∼0.37, 0.29, 0.34 and 0.25 eV, respectively. The results demonstrated that the Li-stuffed LCLN garnet could be a suitable host for UV excitable multicolor phosphors. • ∼900–1000 °C is an appropriate temperature for precursor calcination to derive Li 6 CaLa 2 Nb 2 O 12 (LCLN) garnet. • The LCLN host is suitable for luminescence purposes. • The photoluminescence of Pr3+, Sm3+, Tb3+ and Dy3+ activators was comprehensively elaborated in LCLN. • The concentration quenching of Sm3+ luminescence in LCLN is dominantly resulted from electric dipole-dipole interaction. [ABSTRACT FROM AUTHOR]