Influence of Nd3+ modifying on 80TeO2–xZnO–(20−x)Na2O ternary glass system

Abstract

In this study, the ternary system of TeO2–ZnO–Na2O (TZN) with a fixed TeO2 content of 80 mol. % and with a varied ZnO and Na2O content of totally 20 mol. % was examined for thermal/mechanical properties, Raman and x-ray absorption fine structure (XAFS) spectra, and the evolution of medium distance (correlation length) of order, called blob size here, given from low-frequency Raman spectra and longitudinal/transverse sound velocities as a function of ZnO concentration. The TZN glasses were doped with Nd2O3, and the effects of Nd doping on the above-mentioned properties were reported. High-temperature in situ x-ray diffraction experiments were also conducted to know possible oxygen coordination numbers of these main-constructive cations from crystalline phases precipitated at elevated temperatures. According to the information, the evolution of blob size of Nd-doped and non-doped TZN glasses was attempted to be predicted with a term of theoretical volume of their molar unit constructed with cation–oxygen polyhedra of TeO3, TeO4, ZnO4, ZnO5, NaO4, and NaO5. A transition region due to the structural change owing to the coordination numbers of Te–O and Zn–O was elucidated concerning density, molar volume, and Poisson ratio. XAFS spectroscopy revealed that the ZnO component had different polyhedra of ZnO4 and ZnO5, whose ratio was dependent not only on ZnO concentration but also on whether Nd3+ ions were doped or not. Based on the information taken from a variety of observations, our preliminary analysis suggested that the different mechanical properties between the doped and non-doped glasses were explained by five-coordinated zinc in the glasses. Possible molecular models shall be given for lower and higher ZnO concentrations in TZN glasses.

High‐Temperature Investigation of TeO2–Na2O–ZnO Glasses

“…Comparing the results to previously obtained DSC results in Table 1 (more detailed in Ref. [15]), it seems that around 295 °C, near the glass transition temperature for the Nd-TZ17.5N2.5 glass, the surface crystallization seems to slightly disappear with a broadening of the 41.5°peak, which is evidence that the surface crystallization observed was a consequence of the reaction with atmospheric humidity. At 355 °C, which is near the on-set crystallization temperature for this glass, the low 2θ angles baseline is less slanted and new peaks appear especially from 56°t o 62°, which show the precipitation of (▾) Na 2 ZnO 2 and (#) Na 10 Zn 4 O 9 phases.…”

“…This is the other reason we decided to have the same heat treatment as our previous study. [15] High-temperature in situ XRD (HT-XRD) experiments were performed with an X-ray diffractometer (PANalytical, X'pert Pro MPD) by use of Cu Kα radiation (λ ¼ 1.5406 Å). Powdered samples were set up in a heating cell on top of a platinum holder for in situ heating purposes.…”

“…This discovery shows that the first crystalline phases appearing at around T c1 are sodium related (even if there are still some α-TeO 2 , ZnO, and Zn 2 Te 3 O 8 crystalline phases associated), while the second crystalline peak is mainly zinc oxide Table 1. CN and obtained relevant temperatures (glass transition temperature T g , on-set crystallization temperature T x , first crystallization peak T c1 , [15] second crystallization peak T c2 , and their respective intensities (H Tc1 and H Tc2 ) and ratio). and tellurium oxide related.…”

“…[11][12][13][14] In line with this topic, our group studied and published a detailed analysis of glassy local structure by means of Raman spectroscopy and X-ray absorption fine structure (XAFS) experiments on ternary TeO 2 -ZnO-Na 2 O (TZN)-based glasses. [15] In terms of structural evolution, pure TeO 2 glasses are formed of four oxygencoordinated tellurium (TeO 4 ) polyhedra linked by their edge-sharing chains. The evolution of structures with addition of modifiers was compiled thanks to studies on different TeO 2 -based systems.…”

“…It was found out that the local structure of the TeO 2 changes, going from a TeO 4 polyhedra to a three oxygen-coordinated tellurium (TeO 3 ) polyhedra with an intermediate step of TeO 3þ1 polyhedra, breaking the network-forming TeO 4 chains, which was evidenced in connection with decreasing the exceptional nonlinear optical properties of these glasses. [16][17][18][19][20][21][22][23][24] In our previous paper [15] on the TZN glasses, the composition was as follows: TeO 2 content was fixed to 80%mol while ZnO and Na 2 O contents were varied in totally 20%mol. The thermal/mechanical properties, Raman and Zn-XAFS spectra, and the evolution of medium distance (correlation length) of order, called blob size here, given from low-frequency Raman spectra and longitudinal/transverse sound velocities as a function of ZnO concentration were used to define as much as possible the local changes of the glasses.…”