时　间：11月25日14:00

地　点：科技创新大楼C501

报告人：Prof. Marco Bettinelli

报告题目：Tb³⁺-Eu³⁺ energy transfer in oxide materials

Abstract:

Despite numerous studies over the years, energy transfer processes are still interesting from both a fundamental and an applied point of view, as transfer processes in pairs of ions and from the host to luminescent ions are crucial for development of innovative phosphors, scintillators and materials for solar cells. Here I will present results on these processes, concentrating on the ion pairs Tb³⁺-Eu³⁺ in eulytite phosphate hosts.

Eulytite double phosphates A₃M(PO₄)₃ (A=Ca, Sr, Ba; M=La-Lu, Y, Bi) are well known to be isotypic with the mineral eulytine (Bi₄Si₃O₁₂). The emission spectrum of neat Sr₃Tb(PO₄)₃ upon excitation at 337 nm in the levels above ⁵D₃ is dominated by ⁵D₄ emission; no significant emission from ⁵D₃ is observed due to efficient cross relaxation involving the Tb³⁺ levels. On the other hand, the emission spectrum of the same host containing 10 mol% Eu³⁺ upon excitation at the same wavelength (in the Tb³⁺ levels) is dominated by strong emission bands from the ⁵D₀ level of Eu³⁺. This indicates that Tb³⁺®Eu³⁺ energy transfer is clearly present. The excitation spectrum of the Eu^{3+ 5}D₀ emission is dominated by strong Tb³⁺ bands extending in the UV region.

The presence of 10% Eu³⁺ in Sr₃Tb(PO₄)₃ very effectively shortens the ⁵D₄ decay time from 2.68 to 0.20 ms. The decay curve is not far from exponential, indicating that the energy transfer to Eu³⁺ is accompanied by fast energy migration. The efficiency of the energy transfer from ⁵D₄ amounts to 0.93, and the critical distance for the transfer from the ⁵D₄ level of Tb³⁺ is about 7 ?.

The results obtained for the eulytite hosts will be compared with the ones recently obtained for double silicate hosts containing the same Tb³⁺ and Eu³⁺ ions.