Preparation, crystal structure and photoluminescence properties of Ce3+ activated Ba3Y1−yLuyAl2O7.5 phosphors for near-UV LEDs

Abstract

A series of novel blue-green broadband emitting phosphors Ba 3 Y 1-y Lu y Al 2 O 7.5 : Ce 3+ (0 ≤ y ≤ 0.5) were synthesized via the solid state reaction. The crystal structure and the photoluminescence properties were investigated for the application in white light-emitting diodes. The phosphors have two Ba 2+ sites and one Y(Lu) 3+ site with different coordination environment. These phosphors show the good absorption ranging from the ultraviolet to the blue region, the emission spectra contain both blue and green compositions, and the peaks can shift from 478nm to 493nm by changing the doped Lu 3+ concentration, the mechanisms and reasons of the changes of the PL/PLE spectra, fluorescence decay curves and thermal quenching properties have also been studied in detail. The critical distance for Ce 3+ ions in the Ba 3 YAl 2 O 7.5 host was calculated to be 23.85 Å and the energy transfer mechanism occurs among the nearest-neighbor ions. The above results indicate that Ba 3 Y 1-y Lu y Al 2 O 7.5 : Ce 3+ is a good candidate as the blue-green component for near-UV LEDs.

A tunable blue–cyan dual emission phosphor in Ca4−xLu2xHf1−xGe3O12:Bi3+ via forming segregation structure for WLEDs

“…When the lattice constant becomes small, this change will promote the contraction of Bi 3+ ions in the excited state compared with the ground state, which is more likely to occur Stokes shift. A larger Stokes shift leads to smaller activation energy (∆ E ), which is more likely to cause electrons to return to the ground state through non‐radiative transitions, leading to a decrease in luminescence intensity 46 . Because Bi 3+ ions have larger Stokes shift in the sites of Lu 3+ ions, the intensity of Bi 3+ ions in the [Ca 3 Lu 2 Ge 3 O 12 ] segregation is lower than in the [Ca 4 HfGe 3 O 12 ] segregation.…”

“…A larger Stokes shift leads to smaller activation energy (∆E), which is more likely to cause electrons to return to the ground state through non-radiative transitions, leading to a decrease in luminescence intensity. 46 Because Bi 3+ ions have larger Stokes shift in the sites of Lu 3+ ions, the intensity of Bi 3+ ions in the [Ca 3 Lu 2 Ge 3 O 12 ] segregation is lower than in the [Ca 4 HfGe 3 O 12 ] segregation. Of course, variation in intensity may also be influenced by other factors, such as the difference of structure rigidity, and difference of crystallinity.…”

Bismuth‐activated, narrow‐band, cyan garnet phosphor Ca3Y2Ge3O12:Bi3+ for near‐ultraviolet‐pumped white LED application

“…23,[31][32][33][34][35][36][37][38] T in these cases to determine the resin flow ing times corresponding to different infilt Preceramic polycarbosilane polymers as precursors to make ceramic fibers 10,3 trix. [7][8][9]40,41 The chemical and volume ch pany ceramization of the polymer during documented in several studies. A survey of the published literature shows that process modeling of CMCs has been studied by a number of researchers.…”

“…However, the white light illumination produced by this method still exists some problems including low color rendering index (CRI) and high correlated color temperature (CCT), which limits the practical application of WLEDs. [6][7][8][9] To overcome this shortcoming, researchers have proposed a new strategy of mixing the near-ultraviolet (NUV)-LED chips with blue, green, and red phosphors to achieve the white light. [10][11][12][13][14][15] It can obtain not only a superior warm white light but also a higher excitation energy because of its NUV excitation.…”

“…Preceramic polycarbosilane polymers are commonly used as precursors to make ceramic fibers 10,39 and ceramic matrix. [7][8][9]40,41 The chemical and volume changes that accompany ceramization of the polymer during pyrolysis have been documented in several studies. For example, see Refs [39][40][41][42].…”