Speaker
Dr
SIMON OGUGUA
(UNIVERSITY OF THE FREE STATE)
Description
Introduction
Keeping in mind that the unit cell of spinal ZnAl2O4 is made of tetrahedral and octahedral sites, of which upon doping shows different characteristics. Zn2+ occupies the tetrahedral sites, while Al3+ occupies the octahedral sites. When doped with Fe3+, ZnAl2O4 is characterized by two broad emissions with maxima around 485 and 730 nm [1]. To maintain electrical neutrality, charge balancing should be taking into consideration when doping ZnAl2O4, since charge imbalance can lead to charge defects within the material, which can create non-radiative luminescence centers in the material. We have prepared sets of ZnAl2O4 doped Fe3+ phosphors. To investigate the effect of charge imbalance on the luminescence properties of the phosphors, Fe3+ was used to substitute Zn2+ in one instance and Al3+ in another instance. The site occupancy of the Fe3+ ion was investigated.
Results
The two sets of phosphors are represented by the general formula ZnAl(2-x) Fe_x^(3+)O4 (Fe3+ substituting Al3+) and Zn(1-x)Fe_x^(3+)Al2O4 (Fe3+ substituting Zn2+). The structure, morphology and the elemental compositions of the phosphors were determined using X-ray diffraction, field emission scanning electron spectroscopy and energy dispersive X-ray spectroscopy, respectively. The elemental composition, chemical and electronic states of the phosphors were analyzed using X-ray photoelectron spectroscopy. Both photoluminescence (PL), and cathodoluminescence properties of the phosphors were also studied. The luminescence studies showed that the ZnAl(2-x) Fe_x^(3+)O4 phosphors have superior luminescence than the Zn(1-x)Fe_x^(3+)Al2O4 phosphors, as expected. The band gaps of the phosphors were determined from the diffuse reflectance data.
3. Reference
[1] N. Pathak, S.K. Gupta, K. Sanyal, M. Kumar, R.M. Kadama and V. Natarajan. Dalton Trans. 43 (2014) 9313.
Level for award<br> (Hons, MSc, <br> PhD, N/A)?
N/A
Apply to be<br> considered for a student <br> award (Yes / No)?
Yes
Primary author
Dr
SIMON OGUGUA
(UNIVERSITY OF THE FREE STATE)
Co-authors
Prof.
Hendrik Swart
(University of the Free State)
Prof.
Odireleng Ntwaeaborwa
(University of the Witwatersrand)
