Synthesization And Luminescent Properties Of Rare Earths Doped Ca₂BO₃Cl Phosphor And Its Potential Application In White LEDs

White LEDs are regarded as the new revolution in the domain of illumination. It is one of the focus that the phosphors which are used for white LEDs in the region of the luminescent materials. In this research, Eu2+, Ce3+, Tb3+, Eu3+or Sm3+doped Ca2BO3Cl phosphors are synthesized by a high temperature solid-state method, and its luminescent properties are investigated. The results show that the phosphors may have a potential application in white LEDs. The research and results are summarized as follows:Ca2BO3Cl:Eu2+produce a yellow emission under the ultraviolet and blue radiation excitation. Because Eu2+may occupy two types of Ca2+sites, Ca2BO3Cl:Eu2+emits an asymmetrical single intensive band at573nm corresponding to the4f65d1â†'4f7transition of Eu2+. With an increase the Eu2+doping content, the emission intensity of Ca2BO3Cl:Eu2+is influenced, the concentration quenching is obviously observed, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated as2.166nm, which is in good agreement with the value2.120nm derived from the experimental data. The luminescent properties of Eu2+doped Ca2BO3Cl are influenced by CaCl2and H3BO3. Its emission intensity can be enhanced by adding the excess of CaCl2and H3BO3, and the optimal excess mole concentrations are5mol%and15mol%, respectively. White LEDs are fabricated with Ca2BO3Cl:Eu2+and460nm LED chip, and the CIE chromaticity coordinates is (0.339,0.351).Ca2BO3Cl:Ce3+, Tb3+can produce emission color from blue to green under the ultraviolet radiation excitation. Ce3+and Tb3+in Ca2BO3Cl can produce blue and green light, respectively. And their emission intensities firstly increase, then decrease with the increasing Ce3+and Tb3+doping content, and reach the maximum value at3%Ce3+and5%Tb3+, respectively. Ca2BO3Cl:Ce3+, Tb3+can emit color from blue to green by tuning the relative ratio of Ce3+and Tb3+, and the emission intensity of Tb3+in Ca2BO33Cl can be enhanced by the energy transfer from Ce3+to Tb3+. The results show Ca2BO3Cl:Ce3+, Tb3+may be promising tuning emission phosphor for white LEDs.Sm3+, Eu3+or Sm3+/Eu3+doped Ca2BO3Cl phosphor can be excited by the long ultraviolet radiation excitation. Ca2BO3Cl:Sm3+can produce orange-red light (603nm) under401nm radiation excitation. Ca2BO3Cl:Eu3+can show red light (623nm) under392nm radiation excitation, however, it has a low absorption in the region of395-405nm. The emission intensity of Eu3+in Ca2BO3Cl can be enhanced by codoping Sm3+as a sensitizer, and the energy transfer efficiency (Sm3+â†'Eu3+) gradually increases to55%by increasing Eu3+doping content. It is found to be efficient to extend and strengthen the absorption of near-ultraviolet light in the region of395-405nm by codoping Sm3+. Moreover, the chromaticity coordinates of Ca2BO3Cl:Sm3+, Eu3+can also be influenced by the molar concentration of Eu3+, and the emission intensity and CIE can be compared to those of the conventional red phosphor Y2O2S:Eu3+. The result show Ca2BO3Cl:Sm3+, Eu3+may be promising red emitting phosphor for white LEDs.Ca2BO3Cl:Tb3+and Ca2BO3Cl:Tb3+, A+(A=Li, Na, K) phopshors are prepared, and their luminescent properties are investigated.The emission intensity of Ca2BO3Cl:Tb3+can be enhanced about1.61,1.97and1.81times by codoping compersation charge Li+, Na+and K+, respectively, and the CIE chromaticity coordinates of Ca2BO3Cl:Tb3+, A+(A=Li,Na, K) are (0.335,0.584),(0.335,0.585) and (0.335,0.585), respectively. Hence, A+(A=Li, Na, K) may be the optimal charge compensator for Ca2BO3Cl:Tb3+, and Na+has the optimal effect.