Theoretical Calculation of Bond Energy, Self-Reduction Phenomenon, and Photoluminescence Properties of Eu/Ce Single-Doped and Codoped Ba₂CaB₂Si₄O₁₄ Phosphors

Abstract

The self-reduction of Eu3+ to Eu2+ and Ce4+ to Ce3+ can first be found by doping rare earth ions RE (RE = Eu, Ce) in Ba2CaB2Si4O14 (BCBSO). The Eu2+/Eu3+ codoped BCBSO and Ce4+/Ce3+ codoped BCBSO and Eu/Ce codoped BCBSO were synthesized by a high-temperature solid-phase method in air and reducing atmospheres, respectively. By comparing the photoluminescence spectra in air and reducing atmospheres, the self-reduction phenomenon of Eu3+ and Ce4+ in the BCBSO were verified adequately. The theoretical method of the bond energy was used to analyze the occupancy and self-reduction of Eu or Ce ions. The experimental results are in agreement with the theoretical ones. The color tuning phosphors were achieved in BCBSO:Eu and BCBSO:Ce. The codoped system BCBSO:Eu, Ce was studied and it was found that the position and shape of the emission spectra changed with the change in the excitation wavelength, and the change in the corresponding color could be seen from the CIE chromaticity coordinates. Its emission peak shifts from 481 to 595 nm with the increase in the Ce3+ concentration in the codoped system under the excitation of 365 nm. Based on the fluorescence lifetime, the energy transfer process between Eu2+–Ce3+ is proved, and its emission color can be adjusted to a certain extent.

Precisely Manipulating the Self‐Reduction of Manganese in MgGa2O4 through Lithium Incorporation for Optical Thermometry and Anti‐Counterfeiting

“…Hence, the smaller the variation value in the chemical bond energy of the variable valence ions, the more likely they are going to occupy the lattice, and then realize the self-reduction behavior. [3] Herein, the theoretical calculations of the bond energy were performed based on the following equations: [3,4]…”

“…rare-earth ions in LiSrB 9 O 15 and Ba 2 CaB 2 Si 4 O 14 compounds. [3,4] Unfortunately, there are no reports with a detailed discussion of the self-reduction mechanisms of Mn ions via the bond energy theory. Thereby, more attention should be paid to investigate the self-reduction process of Mn ions using this theory.…”

Experimental and Theoretical Studies of the Site Occupancy and Luminescence of Ce3+ in LiSr4(BO3)3 for Potential X-ray Detecting Applications

“…Because the crystal field strength has a strong influence on the outer 5d orbital of Ce 3+ , the 4f–5d transition energies of Ce 3+ may present remarkable variations in different coordination surroundings. Such a structural factor, which is controlled by site occupancy, directly governs the various aspects of the luminescence properties. − Apparently, a clear understanding of the site occupancy of Ce 3+ in the host compound is crucial for the development of novel lanthanide ion-doped luminescent materials with f–d transitions. To the best of our knowledge, a systematic analysis of the crystal field splitting (CFS) and centroid of Ce 3+ 5d energy levels is a good approach for gaining insight into the site occupancies of the doping Ce 3+ ions experimentally. , Furthermore, the first-principles calculations of the energies of f–d transitions corroborate the site occupancies, and those on the formation and transition energies of Ce 3+ ions in different sites give an explanation for the preferential occupancies theoretically. , …”

Tetrahedrally coordinated rigid crystal structure enables partial self-reduction of mixed-valence europium for optical thermometric application

“…33,65 Two Eu 3+ ions heterovalently doped at two Ca 2+ sites create a charge negative vacancy, V′′ Ca (Kröger–Vink notation), near the Eu 3+ ion to maintain charge neutrality. The negative charges in the V′′ Ca vacancy will thermally transmit to the Eu 3+ ion, thus reducing the Eu 3+ to Eu 2+ as suggested by the following expressions: 42,48,66 …”