Local Structure Modulation-Induced Highly Efficient Red-Emitting Ba₂Gd_1–xY_xNbO₆:Mn⁴⁺ Phosphors for Warm WLEDs

Abstract

Modulating the crystal field environment around the emitting ions is an effective strategy to improve the luminescence performance of the practical effective phosphor materials. Here, smaller Y3+ ions are introduced into substituting the Gd3+ sites in Ba2GdNbO6:Mn4+ phosphor to modify the optical properties, including the enhanced luminescence intensity, redshift, and longer lifetime of the Mn4+ ions. The substitution of smaller Y3+ ions leads to lattice contraction and then strengthens pressure on the local structure, enhances lattice rigidity, and suppresses nonradiative transition. Moreover, the prototype phosphor-converted light-emitting diode (LED) demonstrates a continuous change photoelectric performance with a correlated color temperature of 4883–7876 K and a color rendering index of 64.1–83.2, suggesting that it can be one of the most prospective fluorescent materials applied as a warm red component for white LEDss. Thus, the smaller ion partial substitution can provide a concise approach to modulate the crystal field environment around the emitting ions for excellent luminescence properties of phosphors toward the modern artificial light.

Dazzling Red-Emitting Europium(III) Ion-Doped Ca2LaHf2Al3O12 Garnet-Type Phosphor Materials with Potential Application in Solid-State White Lighting

“…Then, we measured the PLQY ( η ) of Ca 2 LaHf 2 Al 3 O 12 :50%Eu 3+ phosphors using the following formula − herein L S stands for the sample’s emission spectrum and E S denotes the excitation spectrum with the Ca 2 LaHf 2 Al 3 O 12 :50%Eu 3+ phosphor, while E R represents the excitation spectrum without the Ca 2 LaHf 2 Al 3 O 12 :50%Eu 3+ phosphor. The obtained PLQY value of 64% for the Ca 2 LaHf 2 Al 3 O 12 :50%Eu 3+ phosphor is superior to that for several red phosphors including Li 3 Y 3 Te 2 O 12 :Eu 3+ (PLQY = 61%), Y 2 Mg 2 Al 2 Si 2 O 12 :Eu 3+ (PLQY = 60.5%), Li 6 CaLa 2 Nb 2 O 12 :Eu 3+ (PLQY = 51%), Li 2 TiO 3 :Mn 4+ (PLQY = 31.6%), CaGdAlO 4 :Mn 4+ (PLQY = 45%), and Li 4 AlSbO 6 :Mn 4+ (PLQY = 54.8%) …”

Fluorescence Lifetime-Based Luminescent Thermometry Material with Lifetime Varying over a Factor of 50

“…The Mn 4+ ’s energy level can be interpreted by the Tanabe–Sugano diagram (T–S) (Figure b). To calculate the effects of a crystal field, one can use the crystal field parameter D q along with Racah’s parameters ( B ) and ( C ) , As a consequence, D q , B , and C of SIT:0.003Mn 4+ were evaluated as 1795, 817, and 2827 cm –1 . When D q / B ≥ 2.2, a crystal field is considered strong, so the present crystal field ( D q / B = 2.2) in SIT is strong, which is similar to those of Ba 2 La 2 ZnW 2 O 12 :Mn 4+ ( D q / B = 2.28), La 2 LiSbO 6 :Mn 4+ ( D q / B = 2.32), and Ca 2 LaSbO 6 :Mn 4+ ( D q / B = 2.3) .…”

“…The Mn 4+ 's energy level can be interpreted by the Tanabe− Sugano diagram (T−S) (Figure 4b). To calculate the effects of a crystal field, one can use the crystal field parameter D q along with Racah's parameters (B) and (C) 34,35…”

Synergistic luminescent thermometer using co-doped Ca2GdSbO6:Mn4+/(Eu3+ or Sm3+) phosphors

“…30 Especially, Mn 4+ -activated oxide phosphors have excellent chemical stability, long-wavelength emissions, broad excitation band range (220-580 nm), and can be excited by both commercial blue and near-ultraviolet chips. [31][32][33][34][35] Meanwhile, Eu 3+ and Sm 3+ ions have a 4f n electronic configuration with thermal quenching by multi-phonon relaxation (MPR), while that of Mn 4+ ions occurs by energy-level crossover relaxation (ELCR). 36 Thus, Mn 4+ luminescence is quenched by increasing the temperature more rapidly than those of Eu 3+ and Sm 3+ ions.…”