The investigation of low-temperature routes to novel inorganic pigments
The aim of this project was to synthesise via low temperature routes novel mixed
metal oxide materials which are stable at high temperatures and chemically resistant.
Low temperature routes include synthesis techniques such as sol-gel and coprecipitation.
Zircon is used extensively as a crystal host system for chromophores in the pigment
industry. Sol-gel and co-precipitation techniques for the production of zircon were
investigated with a view to optimising the process to achive shorter firing times and
lower firing temperatures (Chapter 4). Zircon was made by several gel methods and
the structure of the gels investigated using a small angle x-ray scattering technique
(Chapter 3), this method highlights the internal properties of the gel. The sol-gel and
co-precipitation products were fired with, and without a mineraliser and analysed
using x-ray diffraction. It was found that co-precipitation techniques proved more
successful and this approach was transferred to other crystal systems related to
A scheelite phase is formed when zircon is under high pressure and temperature with
the silicon in a tetrahedral site and the zirconium in a dodecahedral site as in zircon.
GeZrO4 and CaWO4 (Chapter 5 and Chapter 6) both minerals have a scheelite
crystal structure at room temperature and pressure. Germanium and silica have the
same oxidation state and are both in the tetrahedral site, but CaWO4 has Ca 2* and a
We" in the dodecahedral and the tetrahedral site respectively. Both scheelite
synthesis routes were optimised using a factorial experimental design experiment.
Pr-GeZrO4 and Cr-CaWO4 were optimised and the resulting methodology transferred