The effect of rare earth (RE³⁺) ionic radii on transparent lanthanide-tellurite glass-ceramics: correlation between ‘hole-formalism’ and crystallization

Abstract

Rare earth (RE) doped transparent tellurite glass-ceramics (GCs) are widely explored for their application as advanced photonic materials. Specifically, the growth of RE based “anti-glass” crystalline phases in transparent GCs...

Effect of Nd2O3 Concentration on Crystallization Mechanism and Third-Order Optical Nonlinearity of Lanthanide-Titanium-Tellurite Glass and Glass-Ceramics

“…Transmission windows of LGTT-Nd0.5, LGTT-Nd1 glass, and GCs are shown in Figure a,b, along with photographs of the samples. The same for LGTT-Nd2 samples is given in our previously published article Figure a,b demonstrates complete transparency of the GCs resulting from 3 h heat-treatment of LGTT-Nd0.5 and LGTT-Nd1 glasses similar to that of their parent glass.…”

“…Our previous study indicates that, with a further increase in Nd 3+ concentration, the upper surface of LGTT-Nd2(GC-36h) GCs mostly contains spherical nanocrystallites of the size ∼120−185 nm at the top surface along with small spherical crystallites of ∼45−50 nm in the bulk volume, resulting in an improvement of transparency. 22 Interestingly, these outcomes exactly corroborate the prediction from particle-size-dependent DSC that simultaneous uncontrolled growth in LGTT-Nd0.5 glass would promote precipitation of bigger crystallites, but controlled crystal growth in LGTT-Nd2 would help in precipitating nanosize crystallites. Moreover, an increase of Nd 3+ concentration not only changes the crystalline morphology of the GCs but also decreases the crystallite size from ∼1.8 μm to 120 nm, facilitating transparency retention of the GCs from approximately 12% to 55% in the visible wavelength region.…”

“…In the field of photonics, the utility of GCs completely depends on its transparency. The literature suggests that the parent glass composition and heat-treatment schedule are the foremost factors that affect the transparency of the GCs. − We have reported that a tellurite glass containing ∼10 mol % of La 2 O 3 can precipitate La 2 Te 6 O 15 “ anti-glass ” crystallites on ceramization, giving transparent GCs. , These “ anti-glass ” crystallites are nonstoichiometric in nature and exhibit oxygen vacancies in their structure. , Most interestingly, these phases are precipitated only upon crystallization of TeO 2 glasses and are not achievable from any other glassy matrix . The “ anti-glass ” crystalline phases (Ln 2 Te 6 O 15 , KNbTeO 6 , Bi 0.8 Nb 0.8 Te 2.4 O 8 , Bi 2 Te 4 O 11 , Te 0.2 Zr 0.3 F 0.9 O 0.55 ) display an intermediate structure between amorphous and conventional crystalline phases because of their long-range cationic (Ln 3+ /Te 4+ /Zr 4+ /Bi 3+ /Nb 5+ ) ordering along with a lack of long-range anionic (O 2– ) ordering. ,,, Previously, Shioya et al reported that transparent GCs containing cubic “ anti-glass ” nanocrystallites KNbO 6 exhibit 3 times enhanced third-order nonlinear susceptibility (χ (3) ) compared to their precursor glass.…”

“…18−20 We have reported that a tellurite glass containing ∼10 mol % of La 2 O 3 can precipitate La 2 Te 6 O 15 "anti-glass" crystallites on ceramization, giving transparent GCs. 21,22 These "anti-glass" crystallites are nonstoichiometric in nature and exhibit oxygen vacancies in their structure. 23,24 Most interestingly, these phases are precipitated only upon crystallization of TeO 2 glasses and are not achievable from any other glassy matrix.…”

“…Our previous study revealed the role of doped RE 3+ ionic radii and "hole-formalism" in the crystallization mechanism of lanthanide-tellurite glass and thereby the retention of transparency in GCs. 22 Hence, it can be assumed that the dopant RE 3+ concentration would also play a significant role in the crystallization mechanism so as to retain the transparency of GCs. Hu et al 28 have reported that on increasing the dopant Nd 2 O 3 concentration from 0.5 to 2.5 mol %, the crystallization tendency of the TeO 2 −Bi 2 O 3 −ZnO glasses was enhanced and GCs lose their transparency.…”