Energy transfer mechanism from Gd3+ to Sm3+ in K3Gd(PO4)2:Sm3+ phosphor

Undoped K3Gd(PO4)(2) and trivalent samarium (0.5-2.5 mol%) doped K3Gd(PO4)(2) phosphors were synthesized by the solid-state method. The phase formation, optical and luminescence properties were investigated by x-ray diffraction (XRD), diffuse reflectance (DR) spectroscopy, and photoluminescence (PL) spectroscopy. The fluorescence decay spectra of the obtained phosphors were also recorded to study the energy transfer from sensitizer (Gd3+) to activator (Sm3+). Energy transfer effects from sensitizer to activator caused by rare-earth ions were mainly observed in the obtained PL and lifetime spectra. The decay curves of K3Gd(PO4)(2) phosphor with different Sm3+ ions concentrations were found to be non-exponential and the data is well fitted with the Inokuti-Hirayama (I-H) model. The energy transfer parameters such as critical distance for the transfer processes were determined. The Commission Internationale de l'Eclairage (CIE) chromatic coordinates and color-correlated temperature were also determined for the prepared phosphor.