Influence of Anion/Cation Substitution (Sr²⁺ → Ba²⁺, Al³⁺ → Si⁴⁺, N^3– → O^2–) on Phase Transformation and Luminescence Properties of Ba₃Si₆O₁₅:Eu²⁺ Phosphors

Abstract

A series of promising cyan, green, and yellow emission (Ba, Sr) 3 (Si, Al) 6 (O, N) 15 :Eu 2+ phosphors were synthesized by a Pechini-type sol−gel ammonolysis method. Variations in luminescence properties and crystal structure caused by the modification of phosphor composition were studied in detail. The prefired temperatures of the precursors play a key role in the process of forming the final products. Under UV light excitation, the as-prepared Ba 3 Si 6 O 15 :Eu 2+ phosphor presents a strong cyan emission located at 498 nm. Moreover, the as-prepared oxynitride phosphors, Eu 2+activated (Ba 1−y Sr y ) 3 Si 6−x Al x O 15−μ N δ (x = 0−1.2, y = 0−0.6), display a broader excitation band covering the entire visible region. Under blue light excitation, Ba 3 Si 6−x Al x O 15−μ N δ :Eu 2+ phosphors show a intense and narrow green emission at 520 nm, and the luminescent intensity can be enhanced by increasing Al content within a certain range. However, (Ba 1−y Sr y ) 3 Si 6 O 15−μ N δ :Eu 2+ phosphors exhibit green (520 nm) to yellow (554 nm) emission with increasing Sr content. Unexpectedly, Eu 2+ doped Ba 3 Si 6 O 9 N 4 -type Ba 3 Si 6 O 15−μ N δ −1300 °C phosphor exhibits a bluish green emission and strong thermal quenching behavior. The (Ba 1−y Sr y ) 3 Si 6−x Al x O 15−μ N δ :Eu 2+ phosphors exhibit a small thermal quenching, and the quantum yields measured under 460 nm excitation could reach up to 89% for green Ba 3 Si 6−x Al x O 15−μ N δ :Eu 2+ phosphor and 71% for yellow (Ba 1−y Sr y ) 3 Si 6x O 15−μ N δ :Eu 2+ phosphor. White LEDs with tunable color temperature and higher color rendering index were fabricated by combining the prepared cyan Ba 3 Si 6 O 15 :Eu 2+ /green Ba 2.91 Eu 0.09 Si 6−x Al x O 15−μ N δ (x = 0.06)/yellow (Ba 0.97−y Sr y ) 3 Eu 0.09 Si 6 O 15−μ N δ (y = 0.4) phosphor and a red phosphor with a UV or blue LED chip, indicating that they are promising phosphors for white LEDs.

Multiple Substitution Strategies toward Tunable Luminescence in Lu2MgAl4SiO12:Eu2+ Phosphors

“…The crystal-field splitting of the Eu 2+ 5d levels can also affect the emission peak shift, affecting the position of the lowest 5d levels. Also, the crystal-field-splitting energy is based on the following equation: ,, In the above equation, D q is the crystal-field-splitting energy, R represents the distance between the central ion Eu 2+ and its ligands, z represents the anion charge, e is the charge of the electron, and r is the radius of the d wave function. If the value of D q is smaller, the emission peak will locate at the higher-energy direction.…”

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

“…Previously, many studies have systematically revealed the relationship between luminescence properties and the local coordination structure of Ce 3+ /Eu 2+ /Bi 3+ ions. These strategies containing a “covalency effect”, “crystallographic sites engineering”, and “component substitutions” have been widely approved to generate long-wavelength light. − Xia’s group has reported plenty of Ce 3+ /Eu 2+ -activated oxide luminescent materials and revealed an underlying mechanism based on “crystallographic sites engineering” and “component substitutions” approaches, such as RbLi­(Li 3 SiO 4 ) 2 :Eu 2+ , Ca 10 M­(PO 4 ) 7 :Eu 2+ , and K 3 YSi 2 O 7 :Eu phosphors. ,− Liu’s group successfully designed “component substitutions” strategies to obtain excellent nitride luminescent materials. − Besides, Li’s group, Wang’ group, Zhang’s group, and Im’s group also reported many photoluminescence-tunable and highly efficient Ce 3+ /Eu 2+ /Bi 3+ -activated luminescent materials based on crystal structure design and component substitution strategies. − These researchers exploited many superior luminescent materials in the visible light region, and the corresponding “structure-luminescence” relationship was revealed. However, the corresponding studies and crystal structure design strategies are still deficient in the exploitation of NIR luminescent materials.…”

The composition engineering of red‐emitting Eu3+‐doped Ca10.5(PO4)7‐type solid solution phosphors and application in LED

“…However, deficiency of red light composition provides a comparatively elevated color temperature (i.e., CCT greater than 4500 K), whereas a lower color rendering index (i.e., CRI less than 75), which greatly limits its application in daily life (such as indoor lighting). [7][8][9][10][11][12][13] Alternatively, a white LEDs, based on near-ultraviolet (near-UV) chips (covered by blue, green, and red color phosphors) is feasible to prepare because its optical performance only depends on the phosphors. 12,14 Therefore, red phosphors perform an essential task in white LEDs with excellent performance.…”