A single-phased tunable emission phosphor MgY2Si3O10: Eu3+, Bi3+ with efficient energy transfer for white LEDs

Abstract

A novel single-phased tunable emitting phosphor MgY₂Si₃O₁₀: Bi³⁺, Eu³⁺ has been synthesized by a conventional high temperature solid-state method. X-ray diffraction (XRD), photoluminescence emission and excitation spectra were utilized to characterize the as-synthesized samples. Under UV-light pumping, MgY₂Si₃O₁₀: Bi³⁺ showed characteristic blue emission corresponding to the ³P₁→¹S₀ transition of Bi³⁺ ions, and MgY₂Si₃O₁₀: Eu³⁺ showed characteristic red emission corresponding to the ⁵D₀→⁷F_J (J = 1, 2, 3, 4) transition of Eu³⁺ ions. Spectra indicate that Bi³⁺ ions occupy two nonequivalent sites in the MgY₂Si₃O₁₀ matrix, namely, Bi³⁺(I) and Bi³⁺(II). The two sites (Bi³⁺(I) and Bi³⁺(II)) exhibit broad emission peaks at 411 nm and 490 nm, respectively. Efficient energy transfer between these two Bi³⁺ sites has been proven using the spectra. The spectral overlap between the emission spectrum of Bi³⁺ and the excitation spectrum of Eu³⁺ allows for resonance-type energy transfer to occur from Bi³⁺ to Eu³⁺. The efficient energy transfer from Bi³⁺ to Eu³⁺via a dipole–quadrupole interaction mechanism is significantly demonstrated by comparing experimental data with theoretical calculations. According to the concentration quenching-method, the critical distance of energy transfer from Bi³⁺ to Eu³⁺ is calculated to be 13.2 Å. As it is a new phosphor, CIE coordinates and CCT temperature, in addition to efficient energy transfer have been also investigated in detail. White light emission for MgY₂Si₃O₁₀: n Bi³⁺, m Eu³⁺ can be realized through controlling the concentrations of Bi³⁺ and Eu³⁺. All of the results indicate that MgY₂Si₃O₁₀: n Bi³⁺, m Eu³⁺ is a potential phosphor for white light UV-LEDs.