Multisite formation in gadolinium doped SrF2 nanoparticles

Abstract Gadolinium doped SrF 2 nanoparticles have been synthesized by the precipitation method and characterized by site-selective optical spectroscopy and electron paramagnetic resonance (EPR) spectroscopy methods at cryogenic temperatures. The type of Gd 3+ centres present in SrF 2 is strongly dependent on the heat treatment parameters – the chosen temperature and gas composition during the annealing. Gd 3+ ions in SrF 2 annealed at temperatures up to 400 °C are mainly incorporated into sites with cubic symmetry. Higher annealing temperatures enable charge compensators to locate in a closer vicinity of the Gd 3+ ion lowering the site symmetry. Oxygen compensated Gd 3+ centres form after heating in air atmosphere, whereas for samples heated at an identical temperature in inert atmosphere interstitial fluorine ions serve as charge compensators. A comparison with previous studies of transparent glass ceramics containing SrF 2 :Gd 3+ shows similar patterns in gadolinium centre formation with the precipitated nanoparticles annealed in inert atmosphere here. The obtained results give a fundamental insight in trivalent defect formation mechanisms in nanostructured SrF 2 systems.