Luminescent Properties of (Sr, Zn)Al₂O₄:Eu²⁺,B³⁺ Particles as a Potential Green Phosphor for UV LEDs

Abstract

Sr 1-x , Zn x ) 1-y (Al 1.98 , B 0.02 )O 4 :Eu y 2+ green phosphor particles for ultraviolet light-emitting diodes (UV LEDs) were prepared by spray pyrolysis and their luminescent properties were investigated with changing the reducing temperature, the concentration of the activator, and the ratio of Sr to Zn. For the Sr(Al 1.98 , B 0.02 )O 4 :Eu 2+ phosphor, pure monoclinic SrAl 2 O 4 phase was formed when the post-treatment temperature was 1100-1200 °C. Over 1300 °C, however, the Sr 4 Al 14 O 25 phase appeared as a minor phase, which induced a blue shift in the emission peak. The highest intensity of Sr(Al 1.98 , B 0.02 )O 4 :Eu 2+ phosphor was achieved when the reducing temperature and the content of Eu 2+ were 1200 °C and 10 mol % of the strontium, respectively. It was found that the substitution of 10-50% Zn atoms instead of the strontium greatly enhanced the 520 nm green emission, especially for the excitation wavelength range from 380 to 420 nm. At the high Zn concentration (x > 0.7), a new blue (460 nm) emission was observed and stable even at ambient temperature. This blue emission disappeared when the Zn content became lower than 0.7. The excitation spectrum of (Sr 1-x , Zn x )(Al 1.98 , B 0.02 )O 4 :Eu 2+ phosphor (x e 0.7) well overlapped with the 460 nm blue emissions. Consequently, it was concluded that the new blue sites successfully played the role of sensitizer for the energy transfer, which is responsible for the enhancement of the luminescence intensity. Finally, the optimized phosphor (Sr 0.6 , Zn 0.4 ) 0.9 (Al 1.98 , B 0.02 )O 4 :Eu 2+ 0.1 showed 185% improved emission intensity compared with that of the Sr 0.9 (Al 1.98 , B 0.02 )O 4 :Eu 2+ 0.1 phosphor under ultraviolet (λ ex ) 393 nm) excitation.

Controllable Synthesis and Luminescence Properties of La(OH)3 and La(OH)3:Tb3+ Nanocrystals with Multiform Morphologies

“…As we know, the PL intensity of the phosphor is strongly influenced by the activator concentration. [41][42][43] The PL intensities for the emission spectra clearly vary with changes in the Tb 3+ -doping concentration. As shown in Figure S6 (Supporting Information), the PL intensity first increases with an increase in the activator concentration, reaching a maximum value at 2 %, and then decreases with a further increase in the doping concentration.…”

Bright Blue Photo‐ and Electroluminescence from Eu2+‐Doped GaN/SiO2 Nanocomposites

“…[31,32] The europium ions in the +2 oxidation states are mostly observed in aluminates and silicate matrices which require synthesis at high temperatures and reducing agents such as H 2 . [33][34][35] To our knowledge there are only two reports on the presence of Eu 2+ ions in GaN-based material, but no characteristic photoluminescence of Eu 2+ was observed. [36,37] The reason might be the existence of only small amount of Eu 2+ in their material, as stated by the authors.…”

Combustion synthesis and luminescent properties of green-emitting phosphor (Sr, Zn) Al2O4: Eu2+, B3+ for white light emitting diodes (WLED)

“…It was clear that the substitution of boron was helpful for increasing the luminescent intensity. The phosphor for the WLEDs should have a good excitation spectrum in the wavelength from 370 to 410 nm [8]. So, the codoping of B 3+ (y = 0.08) greatly enhanced the excitation properties in the wavelength range shorter than 400 nm.…”

“…Q. Su et al prepared SrAl 2 O 4 : Eu 2+ phosphors, and found that it is a good green phosphor for a white LED excited with a UV-LED chip [6]. had increased the efficiency of SrAl 2 O 4 : Eu 2+ and extended its excitation band to a longer wavelength [7,8]. In previous investigations, the added B 2 O 3 is substituted in the AlO 4 framework of SrAl 2 O 4 , resulting in the enhancement of luminescence intensity at low concentration [9,10].…”