Speaker
Mr
Simon. N Ogugua
(UNIVERSITY OF THE FREE STATE)
Description
1. Introduction
Nowadays, phosphors have found applications in solid state lighting, phototherapy, information display technologies, and solar cells, among other things. Rare earth oxyorthosilicates of the form R2SiO5 (R = La, Gd, Y) doped with rare earth elements, have been of interest for the past decades due to their wide band gap, fast decay times, high quantum efficiency, high density and minimal self-absorption. Using urea-assisted solution combustions method, we prepared both single and mixed rare-earth oxyorthosilicates doped with Dy3+ powder nanophosphors.
2. Results
The structures of our phosphors analysed using X-ray diffraction (XRD) confirmed that the phosphors crystalized in the pure monoclinic phases of La2SiO5, Gd2SiO5 and Y2SiO5 or in the mixture of any of the three compounds. We also analysed the morphologies, elemental composition, and the chemical and electronic states of our powders using field emission scanning electron spectroscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) respectively. The photoluminescence (PL) (Fig. 1) measured when the samples were excited using a 325 nm He-Cd laser showed broad blue emission assigned to self-trapped excitons in SiO2 [1] (which were not observed in the PL spectra measured in phosphorescence mode when the samples were excited using monochromatic xenon lamp) and 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+ [2]. The colour purity of the samples calculated using the CIE coordinate calculator confirmed that the phosphors can emit tunable colours and white light. Furthermore, there was even distribution of the atomic and molecular ionic species on the surfaces of the samples as shown in the time-of-flight secondary ion mass spectrometer images in Fig 2.
3. References
[1] C. Itoh, K. Tanimura, N. Itoh. J. Phys. C. Solid State Phys. 21(1988) 4693.
[2] K.G. Sharma, N.R. Singh. New J. Chem. 37 (2013) 2784.
At what level of studies are you currently? (Hons/MSc/PhD)
MSc
Are you currently a postgraduate student? (Yes/No)
Yes
Please provide the name and email address of your supervisor.
Prof. O.M. NTWAEABORWA
ntwaeab@ufs.ac.za
Primary author
Mr
Simon. N Ogugua
(UNIVERSITY OF THE FREE STATE)
Co-authors
Prof.
HENDRIK C. SWART
(UNIVERSITY OF THE FREE STATE)
Prof.
ODIRELENG NTWAEABORWA
(UNIVERSITY OF THE FREE STATE)
Dr
SAMY K.K SHAAT
(UNIVERSITY OF THE FREE STATE)
