Effects of Ce3+ codoping and annealing on phase transformation and luminescence of Eu3+-doped YPO4 nanorods: D2O solvent effect.
Ce(3+)- and Eu(3+)-doped YPO(4) nanorods have been prepared at relatively low temperature (120 degrees C). A detailed investigation of the role of Ce(3+) concentration up to 10 atom % on the luminescence intensity of Eu(3+) in Ce(3+)- and Eu(3+)-doped YPO(4) has been carried out. Phase transformation from a tetragonal to a hexagonal structure occurs with increasing Ce(3+) concentrations, and water molecules are also associated during phase transformation. Thermal study shows that water can be retained up to 800 degrees C in the hexagonal structure. Interestingly, the hexagonal structure returns to the tetragonal structure on annealing above 900 degrees C. As-prepared and 500 degrees C heated samples show uniform sized nanorods, whereas a 900 degrees C heated sample shows distorted nanorods in which pores are present. Initially, the luminescence intensity decreases sharply with increasing Ce(3+) concentrations, even for 2 atom %. This is related to the enhanced nonradiative rate as compared to the radiative rate, since multiphonon relaxation to surrounding water molecules increases. This is not due to the possible oxidation-reduction process between Eu(3+) and Ce(3+) to give Eu(2+) and Ce(4+), as confirmed by X-ray photoelectron spectroscopy and luminescence studies. Then, a significant enhancement of luminescence intensity occurs on annealing above 900 degrees C. This can be ascribed to the loss of water molecules during a phase transformation from the hydrated hexagonal to the dehydrated tetragonal phase. To the authors' knowledge, we for the first time performed a luminescent study with a change of solvent from H(2)O to D(2)O, and significant enhancement in luminescence is found.
Luwang
M Niraj
MN
Department of Chemistry, Manipur University, Imphal-795003, India.
Ningthoujam
R S
RS
Jagannath
Srivastava
S K
SK
Vatsa
R K
RK
D002563:Cerium / Q000737:chemistry*; D017666:Deuterium Oxide / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D049449:Luminescence; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010710:Phosphates / Q000737:chemistry*; D015019:Yttrium / Q000737:chemistry*
D010710:Phosphates; D002563:Cerium; D005063:Europium; D015019:Yttrium; D017666:Deuterium Oxide