Site Occupation of Eu²⁺ in Ba_2–xSr_xSiO₄ (x = 0–1.9) and Origin of Improved Luminescence Thermal Stability in the Intermediate Composition

Abstract

Knowledge of site occupation of activators in phosphors is of essential importance for understanding and tailoring their luminescence properties by modifying the host composition. Relative site preference of Eu for the two distinct types of alkaline earth (AE) sites in BaSr EuSiO ( x = 0-1.9) is investigated based on photoluminescence measurements at low temperature. We found that Eu prefers to be at the 9-coordinated AE2 site at x = 0, 0.5, and 1.0, while at x = 1.5 and 1.9, it also occupies the 10-coordinated AE1 site with comparable preference, which is verified by density functional theory (DFT) calculations. Moreover, by combining low-temperature measurements of the heat capacity, the host band gap, and the Eu 4f ground level position, the improved thermal stability of Eu luminescence in the intermediate composition ( x = 1.0) is interpreted as due to an enlarged energy gap between the emitting 5d level and the bottom of the host conduction band (CB), which results in a decreased nonradiative probability of thermal ionization of the 5d electron into the host CB. Radioluminescence properties of the samples under X-ray excitation are finally evaluated, suggesting a great potential scintillator application of the compound in the intermediate composition.

NUV light induced visible emission in Er3+‐activated NaSrLa(MoO4)O3 phosphors for green LEDs and thermometer

“…As displayed in Figure B, the emission intensity at 423 K was about 76% of the initial intensity at room temperature which demonstrated that the NaSrLa(MoO 4 )O 3 :0.04Er 3+ possessed excellent thermal stability. Besides, to further clarify the thermal stability of NaSrLa(MoO 4 )O 3 : x Er 3+ phosphors, the activation energy was analyzed using the following expression:where I 0 and I present initial emission intensity and the emission intensity at different temperatures ( T ), respectively. Δ E , k , and A are the activation energy, Boltzmann constant and coefficient, respectively.…”

Crystal structure, luminescence properties and application performance of color tuning Y2Mg2Al2Si2O12:Ce3+,Mn2+ phosphors for warm white light-emitting diodes

“…The DFT total energies of Model-1 and Model-2 revealed that Mn 2+ strongly preferred to be at the Mg(1) site over the Mg(2) site (by 1.14 eV). 25 In summary, it is proved that Mn 2+ may have a preference for the dodecahedral sites with eight coordination in YMAS:Ce 3+ ,Mn 2+ . However, so far, there are few characterization methods to directly and clearly detect the chemical environment of Mn 2+ .…”

Advances in Near-Infrared Luminescent Materials without Cr3+: Crystal Structure Design, Luminescence Properties, and Applications

“…Third, the Debye temperature (Θ D ) calculation usually identifies crystal structure rigidity, which is usually determined with a quasiharmonic model. , In order to screen matrixes with stable physicochemical properties and excellent environmental stability, the Debye temperature and effective mass analysis take effect. Finally, optical properties and dynamics calculation can give detailed luminescent properties prediction for involved phosphors.…”