Resonant energy transfer in (Eu3+, Bi3+)-codoped CaZrO3 red-emitting phosphor

Abstract

(Eu³⁺, Bi³⁺)-codoped CaZrO₃ phosphor crystallizing in the orthorhombic structure was synthesized from a mixture of CaCO₃, ZrO₂, Eu₂O₃, and Bi₂O₃ using the solid-state reaction method. The structural and optical properties of this phosphor were investigated using X-ray diffraction analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurements. The effects of Bi³⁺ codoping on the Eu³⁺ emission properties were discussed in detail. Temperature dependence of the PL intensity was also measured between T = 20 and 450 K and obtained a quenching energy of E_q ∼ 0.1 eV. Remarkably, the red emission intensity of Eu³⁺ in the (Eu³⁺, Bi³⁺)-codoped phosphor was enhanced more than 10 times compared to the Eu³⁺ singly doped phosphor, thereby suggesting an efficient resonant energy transfer from Bi³⁺ to Eu³⁺. The asymmetry ratio (⁵D₀ → ⁷F₂)/(⁵D₀ → ⁷F₁) for the Eu³⁺ emission had different values with different Eu³⁺ concentrations, indicating that its local site depends on the Eu³⁺/Bi³⁺ concentration. Comparative discussion was also given on the PL spectra for some red-emitting phosphors, CaZrO₃:Eu³⁺, Bi³⁺, SnO₂:Eu³⁺, and K₂SiF₆:Mn⁴⁺.