Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 13
structure of tiny ‘crystallites’. However, if this were the case the crystallites would be
approximately the size of a unit cell (of the order 1 Å 10 -10 m), and on this scale the
idea of crystallinity has little meaning [4].
2.2.2. Structural theories of glass formation
Various theories have been proposed as to how the arrangement of atoms in space, and
the nature of the bonds between the atoms are related to glass formation, known as the
structural theories of glass formation. The kinetic theory of glass formation, which
disregards any structural factors and deals only with the kinetic of crystallisation below
the melting temperature, is also an important consideration (see section 2.2.3). Both
theories are important when trying to understand the phenomena of glass formation, and a
satisfactory explanation is not possible by considering either alone.
2.2.2.1. Early structural theories
Tammann first investigated the constitution of glasses and regarded them as strongly
undercooled liquids, which to a certain extent agreed with later XRD interpretations. This
general theory of a ‘frozen-in’ liquid-type structure was fairly general, but a good start
for the future direction of thinking [2].