Li Panlai

Luminescence characteristics of Eu 2+ activated Ca 2 SiO 4 Sr 2 SiO 4 and Ba 2 SiO 4 phosphorsfor white LEDs

This paper investigates the luminescence characteristics of Eu2+ activated Ca2SiO4, Sr2SiO4 and Ba2SiO4 phosphors. Two emission bands are assigned to the f–d transitions of Eu2+ ions doped into two different cation sites in host lattices, and show different emission colour variation caused by substituting M2+ cations for smaller cations. This behaviour is discussed in terms of two competing factors of the crystal field strength and covalence. These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes (LEDs) based on ultraviolet chip/phosphor technology.

Luminescent characteristics of Ba3 Y2(BO3)4:Eu3+ phosphor for white LED

Abstract The Ba 3 Y 2 (BO 3 ) 4 :Eu 3+ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5 D 0- 7 F 2 transition of Eu 3+ , under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba 3 Y 2 (BO 3 ) 4 :Eu 3+ phosphor was effectively excited by ultraviolet (UV) (254, 365 and 400 nm) and blue (470 nm) light. The effect of Eu 3+ concentration on the 613 nm emission of the Ba 3 Y 2 (BO 3 ) 4 :Eu 3+ phosphor was measured. The results showed that the emission intensity increased with increasing Eu 3+ concentration, and then decreased. The CIE color coordinates of Ba 3 Y 2 (BO 3 ) 4 :Eu 3+ phosphor were x =0.641 and y =0.359 at 15 mol.% Eu 3+ .

Luminescence characteristics of LiCaBO3:Tb3+ phosphor for white LEDs

A novel green phosphor, LiCaBO3:Tb3+, was synthesized by solid state reaction method, its luminescence characteristics were investigated, and the formation of phosphors were confirmed by X-ray powder diffraction (XRD). Its excitation band extended from 220 to 400 nm, which was coupled well with the emission of UV LED (350–410 nm). It exhibited a strong green emission located at 544 nm with chromatic coordination (0.25, 0.58). The emission intensities of LiCaBO3: Tb3+ phosphor were influenced by varying Tb3+ concentration, moreover, could be enhanced by doping charge compensator Li+, Na+, and K+.

Luminescent characteristics of LiCaBO3:Eu3+ phosphor for white light emitting diode

Abstract LiCaBO 3 :Eu 3+ phosphor was synthesized by high solid-state reaction method, and its luminescent characteristics were investigated. The emission and excitation spectra of LiCaBO 3 :Eu 3+ phosphors exhibited that the phosphors could be effectively excited by near ultraviolet (400 nm) and blue (470 nm) light, and emitted red light. The effect of Eu 3+ concentration on the emission spectrum of LiCaBO 3 :Eu 3+ phosphor was studied. The results showed that the emission intensity increased with increasing Eu 3+ concentration, and then decreased because of concentration quenching. It reached the maximum at 3mol.% Eu 3+ , and the concentration self-quenching mechanism was the d-d interaction according to the Dexter theory. Under the conditions of charge compensator Li + , Na + or K + incorporated in LiCaBO 3 , the emission intensities of LiCaBO 3 :Eu 3+ phosphor were enhanced.

A potential single-phased white-emitting LiBaBO3:Ce3+, Eu2+ phosphor for white LEDs

Abstract Ce 3+ /Eu 2+ co-doped LiBaBO 3 phosphor was synthesized by high temperature solid-state reaction method, and its luminescent characteristics were investigated. The hues of the LiBaBO 3 :Ce 3+ , Eu 2+ phosphor varies from blue to white and eventually to yellow-green by properly tuning the Ce 3+ /Eu 2+ ratio. Under UV excitation, white light was generated by coupling blue and yellow-green emission bands attributed to Ce 3+ and Eu 2+ emissions, respectively. The luminous efficacy of LiBaBO 3 :1%Ce 3+ , 2%Eu 2+ calculated from the emission spectrum was about 290 lm/W.

A novel white emitting phosphor Ca2PO4Cl:Dy3+: luminescence, concentration quenching and thermal stability

A novel white emitting phosphor Ca2PO4Cl:Dy3+ was synthesized by a solid state method. The luminescence, concentration quenching and thermal stability of Ca2PO4Cl:Dy3+ were investigated. Ca2PO4Cl:Dy3+ showed three emission peaks, which were located at 483, 575 and 660 nm. Though the ratio of yellow to blue emission intensities showed a similar value, the intensities of yellow and blue peaks were influenced by Dy3+ concentration, and the concentration quenching effect was observed. The emission intensity of Ca2PO4Cl:Dy3+ as a function of temperature was explored and the emission intensity (at 150 °C) of Ca2PO4Cl:Dy3+ was 90.0% of the value at 25 °C, and activation energy was 0.18 eV. The results indicated that Ca2PO4Cl:Dy3+ might be conducive to development of white LEDs.

Luminescent Characteristics of LiSrBO3:Eu3+ Phosphor for White Light Emitting Diode

LiSrBO3:Eu3+ phosphor is synthesized by a high solid-state reaction method, and its luminescent characteristics are investigated. The emission and excitation spectra of LiSrBO3:Eu3+ phosphors exhibit that the phosphors can be effectively excited by near ultraviolet (401 nm) and blue (471 nm) light, and emit 615 nm red light. The effect of Eu3+ concentration on the emission spectrum of LiSrBO3:Eu3+ phosphor is studied; the results show that the emission intensity increases with increasing Eu3+ concentration, and then decreases because of concentration quenching. It reaches the maximum at 3 mol%, and the concentration self-quenching mechanism is the dipoledipole interaction according to the Dexter theory. Under the conditions of charge compensation Li+, Na+ or K+ incorporated in LiSrBO3, the luminescent intensities of LiSrBO3:Eu3+ phosphor are enhanced.

Effect of Eu3+ contents on structure and luminescence properties of Na3Bi2-x(PO4)3:xEu3+ and Na3Bi1-x(PO4)2:xEu3+ phosphors

Abstract A series of Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ and Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ phosphors were successfully synthesized by solid-state method. The structure and luminescence properties were carefully investigated. The excitation spectra presented an obvious excitation band, and the peak was located at 396 nm, which matched well with the popular emissions from near-UV light-emitting diode chips. With the phase of Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ changing to that of Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ , the intensity of magnetic dipole transition ( 5 D 0 →F 1 ) at 598 nm became stronger than that of electric dipole transition ( 5 D 0 → 7 F 2 ) at 621 nm. Under 396 nm excitation, the chromaticity coordinates and the decay curves of the entitled phosphors were also investigated. Based on all experiments without concentration quenching, we could control the luminescence intensity of the material by adjusting the doping amount of the active ions. All results indicated that Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ and Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ phosphors have potential application as red phosphors in near UV chip-based white light emitting diodes.

Energy Transfer from Ce3+ to Eu2+ in LiSrBO3 and Its Potential Application in UV-LED-Based White LEDs

Ce3+/Eu2+ codoped LiSrBO3 phosphor is synthesized, and its luminescent characteristics are investigated. LiSrBO3:Ce3+,Eu2+ phosphor exhibits varied hues from blue to white and eventually to yellow by resonance-type energy transfer from Ce3+ ion to Eu2+ ion and tuning the relative proportion of Ce3+/Eu2+ properly. Energy transfer mechanism in LiSrBO3:Ce3+, Eu2+ phosphor is dominated by the dipole-dipole interaction, and the critical distance of the energy transfer is estimated to be about 2 nm by both spectral overlap and concentration quenching methods. Under UV radiation, white light is generated by coupling 436 and 565 nm emission bands attributed to Ce3+ and Eu2+ radiations, respectively.

Preparation and luminescence characteristics of Eu2+ activated silicate phosphor

This paper synthesizes the Sr2SiO4 : Eu2+ phosphor by high temperature solid-state reaction. The emission spectrum of Sr2SiO4 : Eu2+ shows two bands centred at 480 and 547 nm, which agree well with the calculation values of emission spectrum, and the location of yellow emission of Sr2SiO4 : Eu2+ is influenced by the Eu2+ concentration. The excitation spectrum for 547nm emission has two bands at 363 and 402 nm. The emission spectrum of white light emitting diodes (w-LEDs) based on Sr2SiO4 :Eu2+ phosphor + InGaN LED was investigated.