Retention of the anatase phase in TiO2 through the use of bauxite and zircon dopants

Abstract

Preserving the anatase phase of TiO2 is of interest due to the photocatalytic activity of this phase, which is generally considered superior to rutile Ti02 due to a higher surface area. The retardation of the anatase to rutile transition through the use of low cost dopants, zircon and bauxite, was investigated. Pressed powder compacts of anatase TiO2 doped with varying levels of bauxite and zircon powders were fired at 1025°C for durations of 2, 3 and 4 hours. X-ray diffraction analysis, Scanning electron microscopy, Energy dispersive X-ray spectroscopy and Raman spectroscopy were used to evaluate the effect these dopants have on the transition to rutile.

It was found that both zircon and bauxite retard the transition to rutile in the solid state. Increasing the level of bauxite dopant consistently increases the preservation of the anatase phase. It was found that at levels of bauxite doping over 5 wt%, over 90% of the anatase phase is retained through 2 hour firing cycles.

Using EDS, zircon particles were observed to nucleate elongated prismatic rutile grains. Whilst XRD analysis showed that the addition of zircon has a marked effect on retarding the overall transition of anatase to rutile, increasing levels of this dopant over 2.5% brings about a reduction in preserved anatase, probably due to increased rutile nucleation. Findings showed Samples doped with 2.5% ZrSi04 retained approximately 95% anatase through 2 hour firing cycles.