Tellurite And Fluorotellurite Glasses For Active And Passive

8. Fibre drawing; MDO 348
Fig. (8.13): EDX spectra from points Q (⎯ crystal) and R (⎯ glass) from fig. (8.12).
It can be seen from these EDX spectra (fig. (8.13)) that the crystal contains less oxygen
and tellurium, and more fluorine and sodium than the glass. The amount of zinc is
approximately the same in both the crystal and the glass. The EDX technique will sample
an area similar to the diameter of the beam (10 µm). The crystal in fig. (8.12) is around 2
µm in diameter, therefore, inevitably some glass will also have been sampled. The
quantification from EDX in cases such as this therefore can only be used to obtain
relative amounts of elements present, i.e. the crystalline phase is fluorine and sodium
rich, and oxygen and tellurium deficient, compared to the glass.
Fig. (8.14) shows an ESEM micrograph of four crystals in the glass fibre of
composition MOF005ii (70TeO2-10Na2O-20ZnF2 mol. %). The fibre was mounted end-
on in epoxy resin, and polished back.