Structure and photoluminescence of Eu³⁺ doped Sr₂InTaO₆ red phosphor with high color purity

The Eu³⁺-doped Sr₂InTaO₆ phosphors were obtained by solid-state reaction method and the phase purity of Sr₂InTaO₆:Eu³⁺ samples were investigated by the XRD patterns. The Rietveld refinements were conducted to further obtain crystal structure information and the results indicate Sr₂InTaO₆:Eu³⁺ samples crystallized in the monoclinic system with a <i>P</i> ₁₂₁ space group. The optical band gap of Sr₂InTaO₆ was calculated to be 3.84 eV by the diffuse reflectance spectra, which are consistent with the result (3.823 eV) of density functional theory. Under 396 nm excitation, the Sr₂InTaO₆:Eu³⁺ phosphor showed a red photoluminescence band centered at about 624 nm due to the ⁵D₀ → ⁷F₂ transition. Monitored at 624 nm, the phosphors showed two wide bands from 200 nm to 500 nm, which originated from the charge-transfer band of Eu³⁺-O^2- and f-f transitions of Eu³⁺ ions. The optimum luminous concentration is 0.12 because of the concentration quenching determined to be a quadrupole-quadrupole interaction. The luminescence decay lifetimes of the Sr₂InTaO₆:Eu³⁺ phosphors were milliseconds. Significantly, the temperature-dependent emission spectra of Sr₂InTaO₆:0.12Eu³⁺ phosphors exhibited good thermal stability and the CIE chromaticity coordinates of Sr₂InTaO₆:0.12Eu³⁺ were (0.6265, 0.3693) with high color purity. The present work demonstrated that the Sr₂InTaO₆:Eu³⁺ red-emitting phosphors show great application in lighting technology.