Porous MAl2O4:Eu2+ (Eu3+), Dy3+ (M = Sr, Ca, Ba) phosphors prepared by Pechini-type sol-gel method: The effect of solvents

In this work, a series of porous Eu2+-doped alkaline earth aluminates phosphors including MAl2O4:Eu2+ (Eu3+), Dy3+ (M = Sr, Ca, Ba) have been prepared by Pechini-type sol-gel approach, using citric acid as chelating ligand and ethylene glycol (or H2O) as solvent. The as-obtained samples were characterized by means of XRPD, FESEM and PL techniques. MAl2O4:Eu2+, Dy3+ (M = Sr, Ca, Ba) phosphors were prepared in a reducing atmosphere (H-2/Ar, 20 + 80%) while MAl2O4:Eu3+, Dy3+ (M = Sr, Ca, Ra) phosphors were obtained in air. Upon changing the molar ratio of citric acid to total metal cations concentration in ethylene glycol can produce spherical phosphors and the higher molar ratio favors the formation of spherical ones. Otherwise, irregular shaped phosphors occur when conducting the reaction in pure H2O. The irregular shaped phosphors have higher emission intensity than those spherical ones observed with the help of excitation spectra, emission spectra and decay curves. (C) 2011 Elsevier B.V. All rights reserved.