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Research article2011Peer reviewed

Crystal Structure and Morphology Evolution in the LaXO3, X = Al, Ga, In Nano-Oxide Series. Consequences for the Synthesis of Luminescent Phosphors

Pazik, Robert; Seisenbaeva, Gulaim; Wiglusz, Rafal J.; Kepinski, Leszek; Kessler, Vadim

Abstract

The LaXO3:Tb3+ (X = Al, Ga3+, In3+) perovsldte nanoparticles were obtained using the nonhydrolytic treatment (Bradley reaction) of the molecular precursors of the La((OPr)-Pr-1)(3), Al((OPr)-Pr-1)(3), Ga((OPr)-Pr-1)(3), In5O((OPr)-Pr-1)(13), and-Tb(acac)(3), respectively. It was shown that crystal structure and morphology evolution in the LaXO3, X = Al, Ga, In nano-oxide series " depended on the size and chemical properties of the X-metal atom. Formation of the LaInO3:Tb3+ nanoparticles is distinctly less thermodynamically demanding on contrary to the LaAlO3:Tb3+ and LaGaO3:Tb3+ since it provided crystalline product directly in the solution synthesis at 202 degrees C, rhich is the lowest reported synthesis temperature for this compound up-to-date. This behavior was ascribed to the effects directly connected with the dopant substitution (exchange of bigger La3+ cation with smaller Tb3+) as well as reduction of the particle size. The size effects are mostly reflected in the expansion of the cell volume, changes of the cell parameters as well as shifting and broadening of the Raman bands. Indirectly, size reduction has also an effect on the luminescence properties through the higher probability of presence of surface and net defects as well as heterogeneous distribution of the Tb3+ ions caused by high surface-to-volume ratio. The prepared nanophosphors show basicallysreen emission With exception of whitegreen in case of the LaInO3:Tb3+. Strong emission quenching was found in the latter case being most likely a consequence of the nonradiative energy transfer between Tb3+ and In3+ as well as the presence of defects. In comparison to the Pechini's method, the LaXO3 nanoparticles required significantly lower annealing temperature (700 degrees C) necessary for complete crystallization. Generally the resulting particles are distinctly smaller (5 to 25 nm) and less agglomerated (50-100 nm) depending on the reaction conditions as well as thermal treatment. For the first time, it was shown that the LaGaO3:Tb3+ nanopowder has crystallized in the hightemperature rhombohedral R (3) over barc phase.

Keywords

oxide nanoparticles; crystallinity; morphology; luminescence; bio-imaging

Published in

Inorganic Chemistry
2011, Volume: 50, number: 7, pages: 2966-2974
Publisher: AMER CHEMICAL SOC