Defect states and kinetic parameter analysis of ZnAl2O4 nanocrystals by X-ray photoelectron spectroscopy and thermoluminescence

Megha Jain,Keun Hwa Chae,Sung Ok Won,Ankush Vij,Manju Manju,Ravi Kumar,Anup Thakur

doi:10.1038/s41598-019-57227-8

Abstract

Defect states in ZnAl2O4 have a significant role in its applicability as a luminescent material. To understand the nature and distribution of defects in its crystal lattice, thermoluminescence (TL) study has been carried out. Excellent TL response is observed from γ- and ultraviolet-irradiated samples at different doses and exposure durations, respectively. Different type of fuels employed in combustion synthesis show a remarkable effect on the trap distribution and hence luminescence properties. Shallow and deep traps are observed in crystals attributed to O− vacancies and F+ centers. The mechanism of trapping, retrapping and recombination have been depicted through schematic band model diagram. X-ray photoelectron spectroscopy indicated the presence of various types of defects specifically AlZn antisite defect, oxygen and zinc vacancies which are further upheld by photoluminescence and Raman spectroscopy. All results when summed up, predict ZnAl2O4 to be a quality material for dosimetry.

Highlights

Defect states in ZnAl2O4 have a significant role in its applicability as a luminescent material
Presence of various defects viz. zinc and aluminium vacancies, AlZn antisite defect, oxygen vacancies and cationic interstitials were indicated by refinement and X-ray absorption near edge spectroscopy
TL response curves of samples irradiated at varying γ-radiation doses and different UV exposure times have inferred the presence of O− defects and F+ centers

Summary

Introduction

Defect states in ZnAl2O4 have a significant role in its applicability as a luminescent material. Various types of ionizing radiations such as α, β, γ, cosmic, ultraviolet (UV) and X-rays can be utilized for the pre-exposure[22,23] Informative parameters such as order of kinetics, trap depth and frequency factor from TL emission must be known so that basic mechanism of TL emission and dosimetric properties of material could be critically analyzed[24]. On irradiating the crystal with a suitable ionizing radiation, free charge carriers are generated which get trapped in these metastable states. Aim of the present study is to gain an insight into effect of ionizing radiation and fuel type on the nature of defects generated and in turn on TL of ZnAl2O4 nanoparticles. Sample prepared using MEA fuel is scripted as S1 and that using urea is scripted as S2 throughout the manuscript

Methods

Results

Conclusion