Gadolinium Doped NaLaF4 Nanocrystals in Glass-Ceramics and Polycrystalline Powders

Abstract

Gadolinium doped scintillators could be efficient neutron detectors with a minimal residual radioactivity and good temperature stability [1]. In this research we analyze localization and properties of Gd3+ dopants in oxyfluoride glass-ceramics containing NaLaF4 nanocrystals and in polycrystalline NaLaF4 powders. Glass samples with the composition 63SiO2-7Al2O3-16Na2CO3-9NaF-5LaF-0.1GdF3 were synthesized by the quench melting method and converted to glass-ceramics by the heat treatment technique. Heat treatment temperatures were selected according to the differential thermal analysis curves. Polycrystalline samples were prepared by solid state reaction method from NaF, LaF3 and GdF3 batch materials. GdF3 concentrations were varied from 0.01 to 1 mol%. NaLaF4 nanocrystals have been observed in glass-ceramics and polycrystalline samples by X-ray diffraction measurements. Photoluminescence and cathodoluminescence spectra show a peak around 315 nm, which originates from 6P7 /2 → 8S7/2 energy level transition of the Gd3+ ion. EPR measurements of the glass samples show the Gd3+ spectrum of disordered environment, however in glass-ceramics the EPR spectra have fine structure characteristic to the specific crystallite. EPR measurements of NaLaF4 powders with different concentrations of Gd3+ showed that the EPR spectrum consists of superposition of at least two paramagnetic centres. Reference [1] Watt, David Edwin, and Dennis Ramsden. High Sensitivity Counting Techniques: International Series of Monographs on Electronics and Instrumentation. Vol. 20. Elsevier, 2014. Acknowledgement Financial assistance to the first author from the Baltic-American Freedom Foundation is gratefully acknowledged.