Eu2+在磷酸镧中的发光及Ce3+→Eu2+的能量传递

采用高温固相反应合成了LaPO₄:Eu²⁺和LaPO₄:Ce³⁺,Eu²⁺样品,报道了Eu²⁺在LaPO₄中的发光性质和Ce³⁺→Eu²⁺的能量传递现象。文中探讨了Ce³⁺→Eu²⁺的能量传递机理,根据Dexter电多极相互作用的理论证明其为偶极子偶极子相互作用的共振能量传递。

Luminescence of Eu2+ and Energy Transfer from Ce3+ to Eu2+ in Lanthanum Phosphate

A new luminescence material-LaPO₄ doped with Eu²⁺ and Ce³⁺ was prepared by high temperature solid state reaction. And the optical properties of Eu²⁺ activated and Ce³⁺,Eu²⁺ coactivated lanthanum phosphates were investigated by using photoluminescence(PL) measurements. Emission spectrum of LaPO₄:Eu²⁺ recorded at room temperature with 324nm excitation shows a broad emission band centered at 423nm.And it is possible to determine the distribution of this broad emission band in the spectrum associated with transition from the 4f5d level of Eu²⁺ ion. The excitation spectrum of Eu²⁺ activated lanthanum phosphate recorded at room temperature monitoring 423nm emission exhibits absorption in UV region (220～400nm) assigned to the 4f→5d transition of Eu²⁺ ion. Lanthanum phosphate doped with Ce³⁺ was also prepared by high temperature solid state reaction. The room temperature photoluminescence spectra of LaPO₄:Ce³⁺ show the broad emission and excitation band of Ce³⁺ ion,around 342nm and 284nm,respectively. From these spectra above, it's possible to deduce that energy transfer between the Eu²⁺ and Ce³⁺ ion will probably happen because of the well overlapping between Ce³⁺ emission and Eu²⁺ excitation. And it's well proved in the excitation spectrum of LaPO₄ coactivated by Eu²⁺ and Ce³⁺ at room temperature, monitoring Eu²⁺ emission. This spectrum shows a strong absorption band of Ce³⁺, ranging over 220～340nm, in addition to original f→d transition of Eu²⁺(220～400nm). That is to say there happens a sensitization of Eu²⁺ by the presence of Ce³⁺ ion. The Eu²⁺ emission intensity of LaPO₄:Ce_0.01³⁺, Eu_0.01²⁺ is 5.6 times higher than that of the corresponding phosphor activated by Eu²⁺ only. A series of LaPO₄:Ce_0.01³⁺, Eu_x²⁺ were prepared to study the mechanism of the energy transfer between the Eu²⁺ and Ce³⁺ ion. The emission spectra of the LaPO₄:Ce_0.01³⁺, Eu_x²⁺ at room temperature were measured. The relationship between the Ce³⁺ donor emission intensity and the Eu²⁺ acceptor concentration was fit to the d→d (dipole dipole) energy transfer model for multipole multipole interaction. So it is concluded that the energy transfer between the Ce³⁺ and Eu²⁺ ions in lanthanum phosphate is to be a process of dipole dipole resonance interaction.