Defects in sodalite-group minerals determined from X-ray-induced luminescence

Adrian Anthony Finch, Henrik Friis Mortensen, Mufeed Maghrabi

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

The luminescence spectra of a suite of natural sodium framework silicates including four different sodalite variants and tugtupite have been collected during X-ray irradiation as a function of temperature between 20 and 673 K. The origin of the emission bands observed in these samples is attributed to F-centres (360 nm), paramagnetic oxygen defects (400 and 450 nm), S2 − ions (620 nm) and tetrahedral Fe3+ (730 nm). Luminescence in the yellow (550 nm) is tentatively attributed to Mn2+, and red luminescence in Cr-rich pink sodalite is possibly from Cr3+ activation. Sudden reduction in luminescence intensities of emission centres was observed for all minerals in the 60–120 K range. Since it is common to all the sodalite-group minerals, we infer it is a feature of the aluminosilicate framework. Sodalite luminescence has responses from substitutions on the framework (e.g. paramagnetic oxygen defects, Fe3+) which give sodalite properties akin to other framework silicates such as feldspar and quartz. However, the presence of the sodalite cage containing anions (such as F-centres, S2 − ions) imparts additional properties akin to alkali halides. The possibility of coupling between Fe3+ and S2 − is discussed. The overall luminescence behaviour of sodalite group can be understood in terms of competition between these centre types.
Original languageEnglish
Pages (from-to)481-491
Number of pages11
JournalPhysics and Chemistry of Minerals
Volume43
Issue number7
Early online date17 May 2016
DOIs
Publication statusPublished - Jul 2016

Keywords

  • X-ray excited optical luminescence (XEOL)
  • Thermoluminescence
  • Sodalite
  • Framework silicates
  • Luminescence

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