Influence of Bi³⁺ content on photoluminescence of InNbO₄:Eu³⁺,Bi³⁺ for white light-emitting diodes

A series of red-emitting phosphors InNbO₄:Eu₃₊,Bi₃₊ was prepared by a high temperature solid-state reaction. The structure, size distribution and luminescence properties of the phosphors were respectively characterized by X-ray diffraction (XRD), laser particle size and molecular fluorescence spectrometer. The XRD results indicate that the phase-pure samples have been obtained and the crystal structure of the host has not changed under the Eu³⁺ and Bi³⁺ co-doping. The test of size distribution shows that the phosphor has a normal size distribution. The excitation spectra illustrate that the dominant sharp peaks are located at 394 nm (⁷F₀→⁵L₆) and 466 nm (⁷F₀→⁵D₂). Meanwhile, the emission spectra reveal that the phosphors excited by the wavelength of 394 nm or 466 nm have an intense red-emission line at 612 nm owing to the ⁵D₀→⁷F₂ transition of Eu³⁺. Bi³⁺ doping has not changed the peak positions except the photoluminescence intensity. The emission intensity is related to Bi³⁺ concentration, and it is up to the maximum when the Bi³⁺-doping concentration is 4 mol%. Due to good photoluminescence properties of the phosphor, the InNbO₄:0.04Eu³⁺,0.04Bi³⁺ may be used as a red component for white light-emitting diodes.