Crystal structure evolution of BaBrCl and BaBrCl:5%Eu up to 1073 K by neutron diffraction

Abstract

BaBrCl:Eu is a promising scintillator material; however, the crystal growth yield must be improved for it to become commercially viable. This study measures strain accumulations in the crystal lattice which can contribute to cracking during post-growth cooling. Neutron diffraction is used to measure the crystal structure of undoped and 5 mol% europium-doped BaBrCl from 303 to 1073 K, approaching the melting point. Rietveld analysis of these data provides the temperature dependence of the thermal and chemical strain in BaBrCl. In particular, anisotropic thermal expansion is measured, with expansion along thebaxis nearly double the expansion along theaandcaxes. Additionally, the chemical strain from the incorporation of europium atoms peaks around 673 K, explaining cracking frequently observed in that temperature range.