Tellurite And Fluorotellurite Glasses For Active And Passive

Abstract
Glasses systems based on TeO2-ZnO-Na2O (TZN), TeO2-WO3, and TeO2-Na2O-ZnF2 are
reported here, with a number of other components added (PbO, GeO2, Nb2O5, Bi2O3,
Er2O3, Yb2O3, PbF2, and ErF3).
Glass formation was shown for the first time, to this author’s knowledge, in the
ternary system (90-x)TeO2-10Na2O-xZnF2 for 5 ≤ x ≤ 30 mol. %. Glass stability (Tx-Tg)
was found to increase with ZnF2 addition, reaching a plateau of around 161°C at x = 25
mol. %. This could be due to competition of various phases to crystallise (NaZnF3 and
Zn2Te3O8) as the eutectic is approached, with fluoride addition. These glasses are the
most stable ZnF2 containing tellurite compositions reported to date, to the author’s
knowledge.
As-received ZnF2 batch material was shown to contain a significant proportion of
Zn(OH)F, identified by XRD. The as-received ZnF2 was fluorinated with (NH4)HF2,
which produced a substantially more phase pure powder, with oxygen levels reduced
from around 13.2 to 3.1 at. % from XPS spectra. By calculation from the O1s XPS peaks,
the proportion of Zn(OH)F was reduced in the powders from 39.7 to 9.4 mol. %.
A number of absorption bands in the infrared were identified by FTIR for the TeO2 -
ZnO-Na2O glasses due to intrinsic lattice vibrations (visible in a 0.2 mm sample), and
extrinsic impurity absorption, including: free OH (≈ 3.0 µm ≡ 3300 cm -1 ), weakly
hydrogen-bonded OH (≈ 3.3 µm ≡ 3060 cm -1 ), and strongly hydrogen-bonded OH (≈ 4.8
µm ≡ 2090 cm -1 ).