This paper describes a computational study of the mixed metal fluorides
LiCaAlF6 and
LiSrAlF6, doped with
divalent (Pb2+, Co2+ and
Ni2+),
trivalent (Cr3+, Fe3+ and
Y3+) and
tetravalent (Si4+) ions. For each of the frameworks, all three cation sites were considered, as well
as a range of charge compensation mechanisms. For the divalent dopants,
substitution at the divalent host site is preferred, whilst for the trivalent dopants,
Co3+ and
Fe3+ prefer
the Al3+
site, and Y3+
shows behaviour similar to the rare earths. Finally, it is found that
Al3+ is the preferred site
for substitution by Si4+
in both host frameworks.
In this paper we investigate optical properties and size distribution of the nano-colloids made of trivalent rare-earth ion doped fluorides: holmium and ytterbium, thulium and ytterbium, and erbium and ytterbium co-doped NaYF 4 . These materials were synthesized by using simple co-precipitation synthetic method. The initially prepared micro-crystals had very weak or no visible upconversion fluorescence signals when being pumped with a 980-nm laser. The fluorescence intensity significantly increased after the crystals were annealed at a temperature of 400 0 C -600 0 C undergoing the transition from cubic alpha to hexagonal beta phase of the fluoride host. Nano-colloids of the crystals were made in polar solvents using the laser ablation and ball milling methods. Size analyses of the prepared nano-colloids were conducted using a dynamic light scatterometer and atomic force microscope. The nano-colloids were filled in holey PCFs and their fluorescent properties were studied and the feasibility of new a type of fiber amplifier/laser was evaluated
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