Mid‐IR transparent TeO₂‐TiO₂‐La₂O₃ glass and its crystallization behavior for photonic applications

Abstract

In this report, effect of enhanced rare earth (La2O3) concentration on substitution of TeO2 within ternary TeO2‐TiO2‐La2O3 (TTL) glass system has been studied with respect to its thermal, structural, mechanical, optical, and crystallization properties with an aim to achieve glass and glass‐ceramics having rare‐earth‐rich crystalline phase for nonlinear optical and infrared photonic applications. DSC analysis (10°C/min) demonstrates a progressive increase in glass‐transition temperature (Tg) from 359 to 452°C with the increase in La2O3 content. Continuous glass network modification with transformation of [TeO4] to [TeO3/TeO3+1] units is evidenced from Raman spectra which is corroborated with XPS studies. While mechanical properties demonstrate enhancement of cross‐linking density in the network. These glasses exhibit optical transmission window extended from 0.4 to 6 μm with calculated zero dispersion wavelength (λZDW) varying from 2.41 to 2.28 μm depending upon La2O3 content. Crystallization kinetics of TTL10 (80TeO2‐10TiO2‐10La2O3 in mol%) glass has been studied via established models. Activation energy (Ea) has been evaluated and dimensionality of crystal growth (m) suggests formation of surface crystals. Glass‐ceramic with crystalline phase of La2Te6O15 has been realized in heat‐treated TTL10 glass samples (at 450°C). As predicted from DSC analysis, FESEM study unveils the formation of surface crystallized glass‐ceramics.

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

“…Figure shows the differential scanning calorimetric (DSC) curves at a heating rate ( β ) of 10 K min −1 of TTLG, TTLGH1, and TTLGH2 glass samples. Characteristic temperatures such as glass transition region ( T g ), onset crystallization temperature ( T x ), and peak crystallization temperature ( T p ) obtained from DSC thermographs are shown in Table . For the present series of glass, the value of T g is around 430 °C, whereas the value of T x ranges from 470 to 472 °C.…”

“…In general, an increase in the concentration of modifier components in the tellurite glass composition increases the conversion of TeO 4 structural units into TeO 3 /TeO 3+1 units containing NBOs that are coordinated to the modifier cations . In an earlier effort, authors identified the role of La 2 O 3 as a network modifier in the titanium tellurite glass (i.e., TTL10: 80TeO 2 –10TiO 2 –10La 2 O 3 ) from the variation in the intensity of high‐frequency Raman shift regions resulted due to the depolymerisation of the network structure through the formation of TeO 3 and TeO 3+1 units over TeO 4 units . The comparison of Raman spectrum of TTLG glass with the TTL10 glass (Figure S‐VI(c), Supporting Information) reveals that the Gd 3+ ions also play the similar role of La 3+ ions in the network of TTLG glass.…”

“…[8] Low phonon energy (750-780 cm À1 ), lower melting temperature (850-950 C), and substantial thermal stability (60-120 C) with considerable mechanical and chemical durability offer the tellurium oxide (TeO 2 )based glass systems as the most appropriate candidates for the development of transparent GCs for the various photonic and optical applications. [9,10] However, the emphasis on the development of transparent tellurium oxide-based GCs for various applications is limited to date owing to the difficulties in identifying the suitable chemical composition of glasses to achieve transparent GCs. [11][12][13][14][15][16][17][18] For example, attempts have made on the development of transparent tellurite GCs from 70TeO 2 ─15Nb 2 O 5 ─15R 2 O (mol%) (where R: Li, Na, and K) glass system for their application as nonlinear optical materials.…”

“…[16] In view of the aforementioned discussions, this study aims to develop transparent TeO 2 -based GCs containing a lanthanide tellurite (La 2 Te 6 O 15 )-type nanocrystalline phase. In the previous attempt, authors have reported a La 2 Te 6 O 15 -type "anti-glass" phase from (mol%) 80TeO 2 ─10TiO 2 ─10La 2 O 3 (TTL10) glass composition upon ceramization at 450 C for 3 and 24 h. [9] Nevertheless, the GC was opaque in nature. According to Fujimoto et al, the crystalline sizes of anti-glass (Ln 2 Te 6 O 15 ) phases reduce with the reduction of the cationic radius of lanthanides.…”

Crystallization kinetics of Al2O3-26mol%Y2O3 glass and full crystallized transparent Y3Al5O12-based nanoceramic

“…The peak crystallization temperature T p increases from 950 ℃ to 967 ℃ when the heating rate increases from 5 ℃⋅ min − 1 to 40 ℃⋅ min − 1 . The peak crystallization temperature and corresponding heating rate are used to estimate the crystallization activation energy E a through established models such as Kissinger, Augis-Bennett, and Ozawa models [32,33].…”