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Highly transparent Lu2O3 ceramics were prepared by using co‐precipitation combined with vacuum sintering method with ZrO2 as sintering aid. The effect of ZrO2 on densification, transmittance, and microstructure evolution of the Lu2O3 ceramics was carefully studied. It was found that the addition of ZrO2 was very effective in improving densification of Lu2O3. The highest transmittance (at 600 nm) of the 3 at.% ZrO2 doped Lu2O3 ceramic (1.6‐mm thickness) sintered at 1800°C reached 80.1%. Microstructural inhomogeneity was found after vacuum sintering with larger grain sizes at the central. The microstructural inhomogeneity mainly occurred in the final stage of sintering. Doping ZrO2 mitigated microstructural inhomogeneity and decreased markedly the grain size of Lu2O3 ceramics. Raman measurements indicated that the disordered structure was formed due to oxygen vacancy, and the oxygen vacancy concentration at the central was higher than at the peripheral. The oxygen vacancy concentration gradient is the dominant factor governing nonuniform microstructure evolution during vacuum sintering. Furthermore, a uniform microstructure was obtained by the inhibition of oxygen vacancy formation by the Lu2O3/ZrO2 double powder bed. [ABSTRACT FROM AUTHOR]

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]

Recently, study on Cr3+‐doped zinc gallate and zinc gallogermanate persistent phosphors has become a hot topic in persistent luminescence and bio imaging areas, because of their near infrared (NIR) emission and long afterglow. However, regulation of efficient traps and improvement of persistent luminescence through bottom‐up design are the key challenge. Here, we recommend a new paradigm of chemical unit co‐substitution with [Mg2+‐Ge4+] substituting for [Ga3+‐Ga3+] in ZnGa2O4, which contributes to the opposite charged and distorted octahedral defects of MgGa′ and GeGa· in pair around the CrN2 ions. The formed defect clusters of MgGa′‐CrN2‐GeGa·, which are closely related to the trap depth, can be accurately regulated through varying the doping content of Mg2+/Ge4+ in the resulting spinel solid solutions of ZnGa2−x(Mg/Ge)xO4:Cr3+ (x = 0–1.25). Moreover, the defect clusters cannot only store and recharge visible and UV radiations that contributes to the long lasting NIR persistent luminescence but also can enhance the NIR emission intensity at ~695 nm. The persistent luminescence induced by UV light excitation exhibits an improvement at a deeper trap depth, but it follows an opposite law through visible light excitation. The prepared nanoparticles have the advantages of intense NIR emission, long lasting afterglow, and excellent rechargeability for visible/UV radiations, so they are the potential nanoprobes for long‐term bio imaging in living animals. [ABSTRACT FROM AUTHOR]