Structural, optical and thermoluminescence study of annealed zinc aluminate spinel nanophosphor

The paper is focused on the structural, optoelectronic properties, and thermoluminescence behaviour of annealed zinc aluminate nanophosphor prepared by green synthesis. The samples were characterized by powder X-ray diffraction (PXRD), Fourier Transform Infra-red (FT-IR), UV–visible absorption, photoluminescence (PL), Time resolved photoluminescence spectroscopy (TRPL), and thermoluminescence (TL). The PXRD and Rietveld analysis showed formation of pure zinc aluminate with Fd-3 m space group with average crystallite size ~ 22 nm. FT-IR spectra presented formation of pure zinc aluminate spinel and presence of Al–Zn, Al–O, and Zn–O bonds. UV–visible absorption spectra revealed the involvement of transition bands corresponding to oxygen 2p orbitals, zinc 4s and aluminium 3s orbitals. PL and TRPL spectra revealed intense blue emission at ~ 440 nm with 1.34 ms lifetime of annealed zinc aluminate phosphor at 1100 °C. The Commission Internationale de l’Eclairage (CIE) co-ordinates, CCT (co-related colour temperature), and 98% colour purity of annealed samples was found. Further, the thermoluminescence behaviour of prepared zinc aluminate spinel nanophosphor was studied after ultraviolet irradiation at different radiation exposure time (5–25 min). The thermoluminescence (TL) glow curve exhibits only a peak at 422 K for annealed samples. With longer irradiation time, peak was enhanced and maximum intensity was found for 20 min exposure time. In addition, glow curve peak is shifted to lower temperature side with irradiation time. The TL mechanism is discussed by calculating activation energy, trap depth and other kinetic parameters. The 2nd order kinetics is followed by the samples. The study suggested potential applications of synthesized annealed zinc aluminate phosphor in nano size regime with high colour purity and warm light emission as efficient luminescent material for solid-state lighting and dosimetry applications.