Sk. Khaja Hussain

Eu3+ ion concentration induced 3D luminescence properties of novel red-emitting Ba4La6(SiO4)O:Eu3+ oxyapatite phosphors for versatile applications

A series of Eu3+ ions activated Ba4La6(SiO4)6O (BLSO:Eu3+) phosphors were synthesized by a modified citrate sol–gel process. The structural properties of these phosphors were explored by means of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The XRD patterns confirmed their oxyapatite structure with the space group of P63/m after annealing at 1400 °C. The scanning electron microscope image exhibited the irregular morphology of BLSO:Eu3+ particles and the elemental mapping confirmed that the Eu3+ ions were distributed homogeneously on the La3+ ion sites. Photoluminescence (PL) excitation spectra of BLSO:Eu3+ exhibited the charge transfer band (CTB) and intense f–f transitions of Eu3+ ions in the violet and blue wavelength regions. The CTB intensity decreased and the f–f transition of Eu3+ ions increased with increasing the Eu3+ ion concentration due to the presence of defects in the 4f and 6h sites of the BLSO host lattice. This feature facilitates the strong absorption in the near-ultraviolet (NUV) region, which is useful for high color rendering index NUV based white light-emitting diodes for display and lighting applications. The PL spectra displayed intense red emission (5D0 → 7F2) along with considerable orange emission (5D0 → 7F1) with good asymmetry ratios and chromaticity coordinates, and exhibited better emission performance than that of commercial Y2O3:Eu3+ phosphors. The three-dimensional PL spectra revealed their strong emission characteristics under UV, NUV and visible excitation wavelengths. The cathodoluminescence properties were also similar to the PL results, confirming that the BLSO:Eu3+ phosphors emit stable red emission under different excitation sources as compared to the commercial Y2O3:Eu3+ phosphors.

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.