Tellurite And Fluorotellurite Glasses For Active And Passive

9. Conclusions; MDO 378
• The as-received ZnF2 was fluorinated with (NH4)HF2 [8, 9], which produced a
highly phase pure powder [7].
Fluorination deposit
• Deposits on the silica liner after fluorination of ZnF2 were identified as
(NH4)3SiF6F and NH4F by XRD.
• A likely attack mechanism of the SiO2, is the initial deposit of NH4F from the
volatilised NH3 and HF , which then reacts with the liner to produce (NH4)3SiF6F.
• It is probable that these reactions create 2 moles of H2O per mole of (NH4)3SiF6F
Melt deposit
produced, which may then re-enter the batch as OH.
• The deposit on the silica liner after melting a TeO2-Na2O-ZnF2 glass in the
glovebox, under a dry, nitrogen rich atmosphere, was identified as TeO2, probably
due to the volatile nature of tellurium fluoride species.
Fluorinated melt
• When (NH4)HF2 was added to a 10 g batch of TeO2, Na2CO3, and ZnF2, and
melted at 800°C, around 50 wt. % of the batch volatilised, leaving a deposit of
partially amorphous and partially crystalline (NaZnF3) phases, identified by XRD.