Unraveling Broadband Near-Infrared Luminescence in Cr3+-Doped Ca3Y2Ge3O12 Garnets: Insights from First-Principles Analysis

In this study, we conducted an extensive investigation into broadband near-infrared luminescence of Cr3+-doped Ca3Y2Ge3O12 garnet, employing first-principles calculations within the density functional theory framework. Our initial focus involved determining the site occupancy of Cr3+ activator ions, which revealed a pronounced preference for the Y3+ sites over the Ca2+ and Ge4+ sites, as evidenced by the formation energy calculations. Subsequently, the geometric structures of the excited states 2E and 4T2, along with their optical transition energies relative to the ground state 4A2 in Ca3Y2Ge3O12:Cr3+, were successfully modeled using the ΔSCF method. Calculation convergence challenges were effectively addressed through the proposed fractional particle occupancy schemes. The constructed host-referred binding energy diagram provided a clear description of the luminescence kinetics process in the garnet, which explained the high quantum efficiency of emission. Furthermore, the accurate prediction of thermal excitation energy yielded insights into the thermal stability of the compound, as illustrated in the calculated configuration coordinate diagram. More importantly, all calculated data were consistently aligned with the experimental results. This research not only advances our understanding of the intricate interplay between geometric and electronic structures, optical properties, and thermal behavior in Cr3+-doped garnets but also lays the groundwork for future breakthroughs in the high-throughput design and optimization of luminescent performance and thermal stability in Cr3+-doped phosphors

Efficient Luminescence from CsPbBr₃ Nanoparticles Embedded in Cs₄PbBr₆

This work was financially supported by the “Advanced Research Center of Green Materials Science and Technology” from The Featured Area Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (107L9006) and the Ministry of Science and Technology in Taiwan (MOST 107-2113-M-002-008-MY3, MOST 107-2923-M-002-004-MY3, and MOST 107-3017-F-002-001), the National Centre for Research and Development Poland Grant (No. PL-TW/V/1/2018), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB20000000), the CAS/SAFEA International Partnership Program for Creative Research Teams, and the NSFC (Nos. U1805252 and 11774345). J.P.A. acknowledges financial support from EPSRC, U.K.Cs4PbBr6 is regarded as an outstanding luminescent material with good thermal stability and optical performance. However, the mechanism of green emission from Cs4PbBr6 has been controversial. Here we show that isolated CsPbBr3 nanoparticles embedded within a Cs4PbBr6 matrix give rise to a “normal” green luminescence while superfluorescence at longer wavelengths is suppressed. High-resolution transmission electron microscopy shows that the embedded CsPbBr3 nanoparticles are around 3.8 nm in diameter and are well-separated from each other, perhaps by a strain-driven mechanism. This mechanism may enable other efficient luminescent composites to be developed by embedding optically active nanoparticles epitaxially within inert host lattices.PostprintPeer reviewe

Structural Confinement toward Giant Enhancement of Red Emission in Mn2+‐Based Phosphors

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Unraveling the Near-Unity Narrow-Band Green Emission in Zero-Dimensional Mn2+-Based Metal Halides: A Case Study of (C10H16N)2Zn1-xMnxBr4 Solid Solutions

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Sensitivity modulation of upconverting thermometry through engineering phonon energy of a matrix

Investigation of the unclear influential factors to thermal sensing capability is the only way to achieve highly sensitive thermometry, which is greatly needed to meet the growing demand for potential sensing applications. Here, the effect from the phonon energy of a matrix on the sensitivity of upconversion (UC) microthermometers is elaborately discussed using a controllable method. Uniform truncated octahedral YF₃:Er³⁺/Yb³⁺ microcrystals were prepared by a hydrothermal approach, and phase transformation from YF₃ to YOF and Y₂O₃ with nearly unchanged morphology and size was successfully realized by controlling the annealing temperature. The phonon energies of blank matrixes were determined by FT-IR spectra and Raman scattering. Upon 980 nm excitation, phonon energy-dependent UC emitting color was finely tuned from green to yellow for three samples, and the mechanisms were proposed. Thermal sensing behaviors based on the TCLs (²H₁₁/₂/⁴S₃/₂) were evaluated, and the sensitivities gradually grew with the increase in the matrix's phonon energy. According to chemical bond theory and first-principle calculations, the most intrinsic factors associated with thermometric ability were qualitatively demonstrated through analyzing the inner relation between the phonon energy and bond covalency. The exciting results provide guiding insights into employing appropriate host materials with desired thermometric ability while offering the possibility of highly accurate measurement of temperature.8 page(s

Comparative first-principles calculations of the electronic, optical, elastic and thermodynamic properties of XCaF3 (X =K, Rb, Cs) cubic perovskites

Srovnávací výpočty prvních zásad elektronických, optických, elastických a termodynamických vlastností krystalů XCaF3 (X = K, Rb, Cs)krychlová perovskita. Tři fluoroperovskites s obecným vzorcem XCaF3 (X = K, Rb, Cs) byly systematicky sledovány pomocí metod prvoprincipielníchComparative first-principles calculations of the electronic, optical, elastic and thermodynamic properties of XCaF3 (X =K, Rb, Cs) cubic perovskites. Three fluoroperovskites with the general formula XCaF3 (X= K, Rb, Cs) have been systematically studied using the firstprinciples methods..

Effects of chemical composition on the structural stability, elastic, vibrational, and electronic properties of Cs2NaLnX6 (Ln = La…Lu, X = F, Cl, Br, I) elpasolites

Elpasolite crystals are very important materials, both from the applied and fundamental points of view. Those elpasolites, which contain rare earth ions with a high atomic number Z, are very much suitable for the low-cost high-performance gamma-ray detection, applications in medicine, food industry, nuclear energy production, processing, and detection of nuclear proliferation. The thermal and structural stabilities are important parameters required for detecting applications, because the performance conditions for such devices are usually very harsh. Since it is widely believed that elpasolites may have even better detection properties, the lack of systematic studies on the elpasolites and thus the unavailability of reliable data on their physical properties and trends in their variation caused by chemical composition considerably hinders search for more efficient new materials. Therefore, to fill in this gap and provide with all essential information about a large number of elpasolites crystals, for the first time, the structural stability, elastic, vibrational, and electronic properties of 60 cubic elpasolite Cs2NaLnX6 (Ln = La, …, Lu, X = F, Cl, Br, I) crystals were consistently calculated in the framework of the same computational approach based on the density functional theory (DFT). Variation of all calculated parameters (such as the lattice constants, elastic constants, Debye temperature, normal vibrational modes frequencies, Mulliken effective charges, bond populations, and band gaps) across the considered groups of crystals was analyzed and several trends, which are important for the search and preparation of new stable materials with improved performance, were identified. © 2020 The American Ceramic Society (ACERS