Effect of Sm3+ concentration and excitation wavelength on spectroscopic properties of GdPO4:Sm3+ phosphor

Highlights: • GdPO₄:Sm³⁺ (x = 1%, 2%, 3% and 5%) phosphors were prepared by combustion method. • The prepared phosphors were identified by several technics. • A spectroscopic study as function of excitation wavelength and Sm³⁺ content was presented. • The energy transfer mechanisms were investigated based on several theoretical methods. • A potential candidate phosphor for solid state lighting applications was presented. -- Abstract: Gd_(1−x)Sm_xPO₄ ((1, 2, 3 and 5 mol%) nanophosphors have been synthesized via combustion route. The phase structure and the morphology of the obtained compounds have been identified by X-ray powder diffraction analysis, FTIR spectroscopy and scanning electron microscopy (SEM). The luminescence properties of the phosphor have been investigated based on photoluminescence excitation and emission spectra, and decay curves. The photoluminescence excitation spectra of the phosphors show large number of excitation bands related to the charge transfer state and 4–4 f electronic transitions of Sm³⁺ and Gd³⁺ ions. The photoluminescence spectra registered under excitation in CTB, ⁶I_J level of Gd³⁺ and the ⁴F_7/2 level of Sm³⁺ show different profiles and emission intensity trends as a function of Sm³⁺ concentrations. The decay time curves have double exponential profiles and the registered lifetimes depend on the excitation wavelength and the Sm³⁺ concentration. The possible cross relaxation channels have been discussed based on the near infrared emission of Sm³⁺ under excitation with 273 nm and 401 nm. The evaluation of emission intensities and decay times curves analysis converge to a dipole-dipole interaction under excitation with 273 nm, while under excitation with 401 nm, a nearest-neighbor ions energies transfer mechanism between Sm³⁺-Sm³⁺ ions is dominant. Cool white and pure orange emissions have been obtained upon excitation with 229 and 401 nm, respectively, which may be suitable candidates for displays and photonic devices.