Energy Transfer From Ce³⁺ To Tb³⁺, Dy³⁺ And Eu³⁺ In Na₃Y（Bo₃）₂

Rare earth ions doped luminescent materials have been attracting much attention for their merits such as high efficiency and energy saving. How to improve the luminous efficiency has an important research significance and practical application value. Energy transfer has always been a hot research topic as one of the methods to improve the luminous efficiency. Due to the parity-allowed4f-5d transition, Ce3+has a broad and strong absorption in the UV range, which make it a very good sensitizer. The locations of Ce3+5d level vary greatly in different matrixes, therefore, the energy transfer or sensitization can only be realized in certain matrixes. It is reported that the matrixes mainly focused on aluminates, silicates or phosphates. However, the host preparation temperatures are mostly in the range from1300℃to1600℃. Na3Y(BO3)2(NYB) is a new borate host material, whose preparation method is simple and the reaction temperature is400-600℃lower than those of the materials mentioned above. In this paper, the main research contents and results are follows:1. A series of NYB:3.0%Ce3+(Tb3+, Dy3+and Eu3+), NYB:3.0%Ce3+, x%Tb3+(Dy3+and Eu3+)(x=0,1.0,3.0and5.0) samples were prepared by solid-state reaction. And their photoluminescence properties were studied in detail. The excitation and emission spectra of NYB:Ce3+, Tb3+revealed that an efficient energy transfer process from Ce3+to Tb3+occurred upon excitation Ce3+into5d level. The decay times of Ce3+5d level indicated that there is efficiency energry transfer from Ce3+to Tb3+, which make transfer energy from UV to green emitting.2. The energy transfer process from Ce3+to Dy3+was studied in detail. The excitation spectra of NYB:Ce3+, and NYB:Tb3+indicated that331nm can only excite Ce3+. The emission spectrum, under331nm excitation, consists of Ce3+emission and Dy3+characteristic emissions. These results confirm the occurrence of energy transfer from Ce3+to Dy+. The decay times of Ce+5d level further confirms that there is efficiency energry transfer from Ce3+to Dy3+. Through the attenuation curve of Ce3+, the lifetime and energy transfer efficiency of Ce3+are calculated.3. The emission spectrum of NYB:Ce+consists of a broad emission bands between380at450nm corresponding to the5dâ†'4f transitions of Ce3+, which is the excitation peaks location of Eu+, indicates that an efficient energy transfer process from Ce3+to Eu3+can occur. The excitation spectra of NYB:Ce3+, and NYB:Eu3+indicated that343nm can only excite Ce3+, upon excitation at343nm, only two broad emission bands ascribed to5dâ†'4f transitions of Ce3+are observed in the emission spectra of NYB:Ce3+, Eu3+. The fact that no characteristic emission peaks of Eu3+appeared under Ce3+excitation, indicating that the effective energy transfer from Ce3+to Eu3+did not take place in NYB.4. The excitation and emission spectra of NYB:Ce3+, Tb3+and NYB:Ce3+, Dy3+revealed that an efficient energy transfer process from Ce3+to Tb3+or Dy3+occurred upon excitation Ce3+into5d level. However, there was no obvious evidence of the existence of energy transfer from Ce3+to Eu3+in NYB. In order to realize the energy transfer from Ce3+to Eu3+, Tb+as an intermediate ion was introduced. Based on the excitation and emission spectra of the comparative study, found that the introduction of the intermediate ion Tb3+, can achieve Ce3+to Eu3+energy transfer. So the UV excitation light could be converted into red emission.