Computer modelling of defect structure and rare earth doping in LiCaAlF₆and LiSrAlF₆

Abstract

This paper describes a computational study of the mixed metal fluorides LiCaAlF 6 and LiSrAlF 6 , which have potential technological applications when doped with a range of elements, especially those from the rare earth series. Potentials are derived to represent the structure and properties of the undoped materials, then defect properties are calculated, and finally solution energies for rare earth elements are calculated, enabling preferred dopant sites and charge compensation mechanisms to be predicted.

Luminescence of Pr-doped LiCaAlF6 and LiSrAlF6 crystals

“…Sr-based colquiriite lattice is more disturbed as compared with Ca-based one. It is known that LiCaAlF 6 and LiSrAlF 6 crystals include both Schottky and Frenkel defects [5]. Interstitial F À ions are the main charge compensative defects in RE 3+ -doped LiCaAlF 6 and LiSrAlF 6 .…”

Thermoluminescence and color center peculiarities of Ce doped LiCaAlF 6 and LiSrAlF 6 crystals

“…Higher thermal F-centers stability in LiCAF may be determined by the higher temperature of ionic diffusion-controlled process occurring at T >0.5 T melt as a rule (melting points are at 750 and 825 °C for LiSAF and LiCAF, accordingly). Experimental data [5] proved that Ce 3+ ions occupy Me 2+ sites (Me=Ca, Sr) and the activator center is ascribed to Ce [4]. Obtained results show that the F-coloration efficiency of both Ce-doped crystals is nearly three times higher than of pure ones.…”

“…the parameter a increases whereas c decreases with temperature increasing. In [4], a potential was fitted for the both structures to predict the form of defect disorder. It was shown that Li i + formation is the most likely form of the defect disorder in both matrices.…”

“…Pure and Ce doped LiCAF and LiSAF crystals were grown in CF 4 atmosphere by Czochralski technique [3]. High purity of raw material, effective water and oxygen traces elimination allowed to obtain crystals without oxigen contaminations.…”

“…TSL study allows to reveal the possibility of Ce:LiCAF and Ce:LiSAF dosimeter applications. We presumed that the energy storage is defined by the preferred Ce 3+ ion disposition and charge compensation defect types [1,2,4]. The paper is devoted to the study of radiation induced defect structure to establish a link between color centers and thermostimulated luminescence peculiarities in Ce doped LiCAF and LiSAF crystals.…”