Glasses are usually synthesized by quenching a melt rapidly
enough to avoid crystallization. Nanocrystalline materials can subsequently
be derived from glasses by controlled crystallization with applying
a tailored heat treatment. Upon the latter, nucleation agents are
widely used to adjust the desired nanostructures. Nano glass-ceramics
often possess intriguing properties. For example, they can be ultratransparent;
that is, they hardly scatter light or possess thermal expansion coefficients
very close to zero. Such properties have a high potential for future
applications in optical devices. In this paper, the role of zirconia
and titania used as nucleation agents in a lithia aluminosilicate
glass is studied on the nanoscale using cutting edge analytical and
imaging techniques performed using the transmission electron microscope.
Precipitation of ZrTiO4 nanocrystals [Nano Lett.200992493] was found earlier to be accompanied by the formation of a circumjacent
diffusion barrier consisting of alumina. In addition to this, here
we study the temporal evolution of the alumina barrier and the size
distributions of ZrTiO4 nanocrystals and lithia aluminosilicate
high-quartz solid solution crystals promoted by the nucleation agent.
In the light of these findings, the theory of self-limited growth
is refined.