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)3upon excitation at 337 nm in the levels above5D3is dominated by5D4emission; no significant emission from5D3is 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 the5D0level of Eu3+. This indicates that Tb3+®Eu3+energy transfer is clearly present. The excitation spectrum of the Eu3+5D0emission is dominated by strong Tb3+bands extending in the UV region.
The presence of 10% Eu3+in Sr3Tb(PO4)3very effectively shortens the5D4decay 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 from5D4amounts to 0.93, and the critical distance for the transfer from the5D4level 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.