Determination of thermoluminescence parameters in nanocrystalline CaAl2O4

• Published in: Journal of luminescence 2020-03, Vol.219, p.116867, Article 116867
• Main Authors: Gartia, R.K., Singh, Moirangthem Nara, Chanu, Lisham Paris, Singh, Thoudam Basanta
• Format: Article
• Language: English
• Subjects: CaAl2O4; Parameterization; Phosphors; Trap levels
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2019.116867

This paper is a critical investigation of trap levels present in nanocrystalline CaAl2O4. The technique of thermoluminescence (TL) is used to determine the trap levels. Unlike most workers, we use Computerized Glow Curve Deconvolution (CGCD) technique to decode the TL curves that enables us to determine all the three key trapping parameters, namely, the activation energy (E), the frequency factor (s) and the order of kinetics (b). Using these as inputs we evaluate the electron lifetime (τ) of charge trapped in different traps. This provides the vital information of the possible use of CaAl2O4 based phosphors for practical application in dosimetry, scintillation and persistent luminescence. The phosphor contains multiple discrete trap levels in the band gap (Eg = 7.4 eV) with trap-depths 0.69 ± 0.02, 0.83 ± 0.01, 0.99 ± 0.02, 1.06 ± 0.02, 1.18 ± 0.03, 1.28 ± 0.02 and 1.41 ± 0.01 eV. The magnitudes of the frequency factors (s) for all the cases are ≈109 that translates the Urbach's coefficient as 23.47 ± 0.14. We believe this work is first of its kind in providing complete parameters of trap levels in CaAl2O4 phosphor. The life times at Room temperature (τ300) of the change in these varies are spread are a wide range of 18 min ≤ τ300 ≤ 1007 years which show that CaAl2O4 based phosphors can be designed for specific application with appropriate trap level modification. This explains the excellent persistence luminescence in CaAl2O4: Eu2+, Nd3+ that will be discussed in detail. •Thermoluminescence of CaAl2O4 shows a number of discrete trap levels.•These trap levels can be anywhere between 0.69 eV and 1.41 eV.•Lifetime (τ) of charge in these varies from hours to 107 years.•CaAl2O4 lattice has potentiality for both persistent luminescence as well as dosimetry.