The
presence of lanthanide-tellurite “anti-glass”
nanocrystalline phases not only affects the transparency in glass–ceramics
(GCs) but also influences the emission of a dopant ion. Therefore,
a methodical understanding of the crystal growth mechanism and local
site symmetry of doped luminescent ions when embedded into the precipitated
“anti-glass” phase is crucial, which unfolds the practical
applications of GCs. Here, we examined the Ln2Te6O15 “anti-glass” nanocrystalline phase growth
mechanism and local site symmetry of Eu3+ ions in transparent
GCs produced from 80TeO2–10TiO2–(5
– x)La2O3–5Gd2O3–xEu2O3 glasses, where x = 0, 1, 2. A crystallization
kinetics study identifies a unique crystal growth mechanism via a
constrained nucleation rate. The extent of “anti-glass”
phase precipitation and its growth in GCs with respect to heat-treatment
duration is demonstrated using X-ray diffraction (XRD) and field emission
scanning electron microscopy (FE-SEM) analysis. Qualitative analysis
of XRD confirms the precipitation of both La2Te6O15 and Gd2Te6O15 nanocrystalline
phases. Rietveld refinement of powder X-ray diffraction patterns reveals
that Eu3+ ions occupy “Gd” sites in Gd2Te6O15 over “La” sites
in La2Te6O15. Raman spectroscopy
reveals the conversion of TeO3 units to TeO4 units with Eu2O3 addition. This confirms the
polymerizing role of Eu2O3 and consequently
high crystallization tenacity with increasing Eu2O3 concentration. The measured Eu3+ ion photoluminescence
spectra revealed its local site symmetry. Moreover, the present GCs
showed adequate thermal cycling stability (∼50% at 423 K) with
the highest activation energy of around 0.3 eV and further suggested
that the present transparent GCs would be a potential candidate for
the fabrication of red-light-emitting diodes (LEDs) or red component
phosphor in W-LEDs.
The transparent TeO2‐based glass‐ceramics (GCs) have yet to achieve the breakthrough in photonic technologies, because of poor understanding in optimizing the growth of nanostructured crystalline phases. In the present investigation, the size effect of phase‐separation‐induced, nanostructured Ln2Te6O15‐based (Ln: Gd, Ho) “anti‐glass” phase in Ho2O3‐modified TeO2‐based TTLG (in mol%, 80TeO210TiO25La2O35Gd2O3) glass has considered to achieve transparent GCs. Raman study of TTLG glass reveals the presence of TeO3, TeO3 + 1, and TeO4 units with average TeO coordination number as 3.49. The formation of nanostructured Ln2Te6O15 phases in GCs is confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Furthermore, TEM analysis confirms that an increase of Ho2O3 concentration has reduced the size of phase‐separated domains in nanoscale with superstructure formation to attain transparent GCs. The superiority of this obtained transparent GCs as photonic material for near‐IR (NIR) to mid‐IR (MIR) range has been established by the realization of enhanced luminescence intensities and bandwidth at ≈2900 nm (Ho3+: 5I6 → 5I7) and ≈2050 nm (Ho3+: 5I7 → 5I8). This study offers an opportunity to fabricate the various accessible lanthanide ions‐doped and/or co‐doped TTLG glass with control over nanostructure, to design a series of GCs which are transparent from visible to MIR range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.