Er3+:NaYb2F7 imbedded fluorotellurite transparent glass ceramic for enhanced upconversion luminescence and related thermometric behavior

Fluorotellurite glass ceramics (GCs) are promising photonic materials owing to their unique characteristic of integration of low cut-off phonon energy of fluorides and the high refractive index of tellurite glasses. Here, appropriate heat treatment to obtain the transparent GC from the parent glass (PG) of TeO2-Al2O3-NaF-CaF2YbF3-ErF3 was established. The XRD, TEM, and spectroscopy techniques were employed to characterize the structure and properties of the as-prepared samples. The single fluoride phase NaYb2F7 crystallized from the PG was confirmed by XRD. TEM images displayed that in the transparent GC the nanocrystals are uniformly distributed in glassy matrix with an average size of about 6 nm. Under the 980 nm NIR excitation, the transparent GC exhibited bright upconversion luminescence in the visible region with intensity enhancement of -73% comparing with the PG. The upconversion fluorescence kinetics were studied, along with the upconversion mechanism analyzed in details. Furthermore, the dependence of upconverted fluorescence intensity ratio (FIR) of the 2H11/2 -> 4I15/2 emission to 4S3/2 -> 4I15/2 emission from Er3+ ions on temperature was studied over a temperature range of 323-548 K. The results have shown that the Er3+:NaYb2F7 imbedded transparent fluorotellurite GC can be favorably employed for temperature sensing.