Synthesis, Characterization and Formation Mechanism of Quasi-Spherical Gd2o2s:Pr3 + Phosphor by Sulfurization of Oxide Powder Using Ammonium Thiocyanate and Argon Gas

Quasi-spherical Gd 2 O 2 S:Pr 3+ green phosphor was successfully synthesized via sulfurization of oxide powders using ammonium thiocyanate (NH 4 SCN) and argon (Ar) gas, which use Gd 2 O 3 , HNO 3 , NH 3 ·H 2 O, Pr(NO 3 ) 3 ·6H 2 O, CO(NH 2 ) 2 and NH 4 SCN as the main starting materials. X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Differential scanning calorimetry-thermogravimetry (DSC-TG), Fourier transform infrared spectrometer (FT-IR) and Photoluminescence (PL) were used to characterize the synthetic products. XRD analysis shows that the as prepared Gd 2 O 2 S powder is pure phase when the calcination temperature is 1000 o C for the precursor and the sulfuration temperature is 650 o C for gadolinium oxide powder. FE-SEM shows that the precursors with uniform spherical structure and the average size of 300 nm can eventually be transformed into quasi-spherical Gd 2 O 2 S powder with the average size of 150 nm by the calcination at 1000 o C for the precursor and the sulfuration at 650 o C for gadolinium oxide powder. Moreover, the formation mechanism of Gd 2 O 2 S has also been proposed. PL analysis shows that the quenching concentration is 1.00%, when the emission spectrum of Gd 2 O 2 S:1.00%Pr 3+ upon excitation at 460nm of blue light exists strong green emission band centered at 513 nm, which belongs to the 3 P 0 → 3 H 4 energy level transitions of Pr 3+ ions and its corresponding lifetime is t=0.62061ms, and the corresponding CIE coordinates are (0.3314, 0.5649).