Tellurite And Fluorotellurite Glasses For Active And Passive

9. Conclusions; MDO 379
• This was possibly due to reaction of the (NH4)HF2 with the batch, producing
volatile compounds (TeF4 and TeF6), or the reaction was sufficiently exothermic
to decompose the melt. This drying route was not pursued further.
Fluorotellurite crystallisation
• Two crystalline phases were identified by XRD from glass 70TeO2-10Na2O-
20ZnF2 mol. % heat treated at 400°C, which were Zn2Te3O8 and NaZnF3 [7].
• The asymmetric DTA crystallisation exotherm was Gaussian deconvoluted into
two peaks at 410°C (NaZnF3) and 421°C (Zn2Te3O8) [7]. The lower temperature
phase was confirmed to be fluorine and sodium rich by EDX analysis, possibly
growing from oxide homogeneous nucleation sites which formed on quenching.
Heat treated Er +3 -doped fluorotellurite glasses
• No crystalline phases were identified in the Er +3 -doped 70TeO2-10Na2O-20ZnF2
mol. % glasses, heat treated at various temperatures and times.
• Even opaque samples exhibited the characteristic amorphous halo, however the
shape of this halo was modified with heat treatment, developing a shoulder, and
growing in intensity, indicating a structural change. However, the crystallites may
have been too small to detect by powder diffraction.