高掺杂Ce3+,Tb3+在正硼酸盐中的发光特性及能量传递

本文利用纳秒技术和一般光谱学技术系统地研究了Ce3+,Tb3+离子在LnBO3(Ln=La,Gd和Y)中的发光特性和能量传递机制.发现在La1-xCexBO3中Ce3+离子的浓度在0.1mol以上才出现明显的浓度猝灭.故对敏化剂Ce3+可以高浓度掺杂.本文对高掺杂下材料的发光特性,Ce3+到Tb3+能量传递的规律和机制进行了系统研究.给出了在正硼酸盐中绿色发光材料的最佳配比.

FLUORESCENCE AND ENERGY TRANSFER MECHANISM OF Ce3+ AND Tb3+ IN LnBO3(Ln=La,Gd,Y)

Fluorescence feature of Ce3+ and Tb3+ in LnBO3 and the energy transfer mechanism from Ce3+ to Tb3+ in borate have been systematically investigated.The quenching concentration of Ce3+ in borate can be very heavy,for example at 0.1 mol and above in LaBO3.The green emission intensity of Tb3+ is best when the concentration of Ce3+ and Tb3+ reaches 0.1 mol in LaBO3.The sensitization process of Tb3+ ions by Ce3+ ions in LnBO3 is mainly energy transfer from Ce3+ ions to Tb3+ ions(5D3 and 5D4)with nonradiative resonance process.Electrons at 5D3 level transit into 5D4 level of Tb3+ ion by cross relaxation.Thus the green emission(5D4-7F7,544nm)intensity of Tb3+ reaches the maximum when the concentration of Tb3+ is at 0.1mol.In the case of heavy doping the blue emission(5D3-7F7)can not be seen.With surveying the fluorescence decay of Ce3+ in borate doped with different concentration of Tb3+,it is found that the experimental results accord well with theoretical values.The mechanism of nonradiative resonance energy transfer is found to be dipole-dipole interaction.The critical transfer distance R0 is approximately 7.7Åand 6.5Åin LaBO3 and GdBO3 respectively.The probability and efficiency of the energy transfer have also been calculated.The efficiency of the energy transfer from Ce3+ to Tb3+ might leach 90% and above in LaBO3 when the concentration of Ce3+ and Tb3+ is at 0.1 mol.Further research has indicated that energy diffuse within the sensitizer(Ce3+)affects the energy transfer process from Ce3+ ions to Tb3+ ions.