Uniformity of Thermoluminescence and Optically Stimulated Luminescence Signals Over the Length of Doped LiMgPO4 Crystal Rods Grown by Micro-Pulling-Down Method.

Barbara Marczewska,Paweł Bilski,Mariusz Kłosowski,Łukasz Boroń,Wojciech Gieszczyk,Marzanna Książek

doi:10.3390/ma14010132

Abstract

The purpose of this work was to systematically assess the distribution of thermoluminescence (TL) and optically stimulated luminescence (OSL) properties along the length of crystals grown by the micro-pulling-down method, in relation to the microstructure and distribution of activators. We analyzed lithium magnesium phosphate (LiMgPO4; LMP) crystals doped with terbium (Tb; 0.8 mol%) or with a combination of thulium (Tm; 0.8 mol% or 1.2 mol%) and boron (B; 10 mol%). Crystals of several centimeters in length and 3 mm in diameter were cut into 20–40 slices, depending on length. For each sample, TL glow curves and OSL decay curves were examined. Optical microscopy and scanning electron microscopy were used to assess the microstructure and elemental composition of several selected samples. Two-dimensional TL readouts were performed to identify the areas with higher and lower signal emission. Our study showed that there may be significant differences not only in LMP sensitivity along the crystal’s axis but also on the surface of the slice. The distribution of activators varies depending on the type of crystals and strongly affects luminescence properties.

Highlights

We examined the uniformity of luminescence properties along crystals grown by the MPD method, using a sample of lithium magnesium phosphate (LiMgPO4 ; LMP), which is one of the several relatively new luminescent materials that could be applied in dosimetry due to high sensitivity to ionizing radiation
Lithium magnesium phosphate crystals doped with Tb and Tm are considered as Lithium phosphate crystals dopedand with
Tm are considered as phosphors thatmagnesium are highly sensitive to ionizing radiation as such are candidates for Lithium magnesium phosphate crystals doped with

Summary

Introduction

In contrast to the well-known Czochralski method, in which the crystal is pulled up after the seed touch, the MPD method involves pulling of the melted material in a downward direction through a microcapillary channel made in the bottom of a crucible [1,2]. This allows crystals to be grown at a relatively high speed and to obtain them within a few hours.

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Conclusion