Properties of Charge Carrier Traps in Lu2O3:Tb,Hf Ceramic Storage Phosphors Observed by High-Pressure Spectroscopy and Photoconductivity

Natalia Majewska,Marek Grinberg,Jumpei Ueda,Sebastian Mahlik,Dagmara Kulesza,Tadeusz Lesniewski,Eugeniusz Zych

doi:10.1021/acs.jpcc.0c04056

Abstract

In this work, the kinetic study of charge carrier trapping processes, photocurrent excitation measurements, and high-pressure spectroscopy investigation of an optically stimulated luminescence (OSL) process in Lu2O3:Tb,Hf ceramics are presented. The OSL process was experimentally and theoretically treated to explain the OSL mechanism and kinetics. The obtained results allowed to propose an energetic structure of the system and a theoretical model that explains the charge exchange between Hf4+ and Tb3+ (upon charging the system). It was shown that the OSL took place via the conduction band and the depths of Hf traps were determined for the thermal (1.36 eV) and optical (2.95 eV) release and the significant difference between these two values was fully justified.

Highlights

It was previously shown[1−3] that Lu2O3:Tb,Hf exhibits an ability of excited carrier trapping when irradiated with ionizing (α, β, γ, and X-rays) or short-wavelength UV radiation.Recovery of the stored energy is possible by thermal (TL)and optical stimulations
The room temperature (RT), photoluminescence (PL), and photoluminescence excitation (PLE) spectra were recorded with a FluoroMax-4P spectrofluorometer (Horiba) equipped with a 150 W xenon lamp as the excitation source and a R928 Hamamatsu photomultiplier as a detector
Trap charging and optically stimulated luminescence (OSL) transient characteristics were measured in Lu2O3:Tb,Hf

Summary

Introduction

It was previously shown[1−3] that Lu2O3:Tb,Hf exhibits an ability of excited carrier trapping when irradiated with ionizing (α, β, γ, and X-rays) or short-wavelength UV radiation.Recovery of the stored energy is possible by thermal (TL)and optical stimulations. Lu2O3:Tb,Hf shows an impressive range of linear dose−response dependence exceeding 7 orders of magnitude.[4] This puts the Lu2O3:Tb,Hf ceramic on a short list of storage phosphors/dosimeters offering to measure both very low (natural background) and very high doses (used in sterilization) with high accuracy. Previous studies[2] have shown that Lu2O3:Tb,Hf may release stored energy as green luminescence of Tb3+ ions upon optical stimulation around [420−430] nm of a charged specimen. This is possible because during carrier trapping, a broad absorption band is formed in the blue-violet range

Methods

Results

Conclusion