Influence of Ho₂O₃ on Optimizing Nanostructured Ln₂Te₆O₁₅Anti‐Glass Phases to Attain Transparent TeO₂‐Based Glass‐Ceramics for Mid‐IR Photonic Applications

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%, 80TeO₂10TiO₂5La₂O₃5Gd₂O₃) glass has considered to achieve transparent GCs. Raman study of TTLG glass reveals the presence of TeO₃, TeO_{3 + 1}, and TeO₄ units with average TeO 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.