Enhanced 5D0 → 7F4 transition and optical thermometry of garnet type Ca3Ga2Ge3O12:Eu3+ phosphors

Abstract

The garnet type phosphors of Eu³⁺ doped Ca₃Ga₂Ge₃O₁₂ were synthesized via conventional solid state reaction techniques. The phase purity and luminescence properties of the fabricated phosphors were characterized by X-ray powder diffraction, photoluminescence excitation and emission spectra, temperature dependent emission spectra as well as luminescence decay curves. The phosphors show enhanced red emission from a ⁵D₀ → ⁷F₄ transition of Eu³⁺ under the excitation of 394 nm. The unusual ⁵D₀ → ⁷F₄ intensity was explained by structural analysis. The emission intensity of the phosphors increases with the concentration of Eu³⁺ until the quenching concentration of 10 mol%. Excited by a pulsed laser of wavelength 610.8 nm, the emission intensity of the ⁵D₀ → ⁷F₄ transition increases monotonously as the temperature increases in the range of 160–360 K. The temperature dependent fluorescence behavior was investigated. The relative sensitivity reaches the maximum value of 3.66% K⁻¹ at 160 K and reaches 1.04% K⁻¹ at 300 K. The results show that the garnet type Ca₃Ga₂Ge₃O₁₂:Eu³⁺ phosphor is a promising material for the application of optical thermometry.