Facile synthesis of Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distribution and photoluminescence

Suppressing the crystallization and plate-like crystallite growth of RE2(OH)(4)SO4 center dot 2H(2)O compound by low-temperature (similar to 4 degrees C) precipitation produced an amorphous RE2(OH)(3.3)(CO3)(0.35)SO4 center dot 2H(2)O precursor (RE = Gd1-xTbx) that can be decomposed to Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distributions upon calcination in air at 1000 degrees C (average particle size similar to 156.9 nm) and in hydrogen at 800 degrees C (average particle size similar to 130.2 nm), respectively. The optimal RE3+ concentration for precursor synthesis was determined to be similar to 0.10 mol/L. Through detailed characterization by XRD, FTIR, DTA/TG, FE-SEM, TEM and particle sizing, the courses of phase/morphology evolution were clarified. Photoluminescence study found that the (Gd0.99Tb0.01)(2)O2SO4 and (Gd0.98Tb0.02)(2)O2S representative phosphors have quantum efficiencies of similar to 16.8% (lambda(ex) = 275 nm) and 38.5% (lambda(ex) = 286 nm), fluorescence lifetimes of similar to 3.70 and 1.75 ms and activation energies for thermal quenching of similar to 0.552 and 0.385 eV, respectively. The values are remarkably larger than those reported for Gd2O2S:Tb, which are considered to be due to higher purity, better crystallization and fewer luminescence-quenching defects of the product. Particularly, the (Gd0.99Tb0.01)(2)O2SO4 phosphor has negative thermal quenching up to similar to 150 degrees C and can retain over 85% of its room temperature emission intensity at 250 degrees C, which may enlighten its application in high-power LEDs. (C) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Automated summary

By suppressing crystallization at low temperature, an amorphous precursor was successfully synthesized and transformed into green phosphor nanopowders with excellent properties. Detailed characterization and photoluminescence study unveiled the evolution during synthesis and fluorescence characteristics of the phosphors.