La(OH)₃:Eu³⁺ and La₂O₃:Eu³⁺ nanorod bundles: Growth mechanism and luminescence properties

Oriented attachment assisted self-assembled three-dimensional (3D) flower-like La(OH)₃:Eu³⁺ nanorod bundles were successfully synthesized by a facile wet-chemical method. Hexamethylenetetramine played an important role in the formation of the hexagonal phase of La(OH)₃:Eu³⁺ with respect to the reaction time and its concentration. No other surfactants or capping agents were used. The calcination temperature did not show any influence on the morphological texture, and the La₂O₃:Eu³⁺ phase was obtained by a subsequent annealing process. The phase formation and morphological properties were confirmed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photoluminescence properties were studied for both the synthesized La(OH)₃:Eu³⁺ and La₂O₃:Eu³⁺ samples, and also compared with that of the solid-state reaction based La₂O₃:Eu³⁺ phosphor. The 3D flower-like La₂O₃:Eu³⁺ nanorod bundles showed an intense red emission due to the hypersensitive ⁵D₀ → ⁷F₂ transition with good asymmetric ratio and chromaticity coordinates. Likewise, a systematic study of the cathodoluminescence (CL) properties was carried out in detail. Furthermore, to estimate the CL potentiality, the La₂O₃:Eu³⁺ phosphor was compared with a commercially available Y₂O₃:Eu³⁺ red phosphor.