Effects of Mg2+ doped TiO2 defect structures on TiO2 anatase-to-rutile phase transition.

Rutile TiO 2 is a competitive white pigment due to its high refractive index and inertness. Uncolored Mg2+ is a promising dopant for the production of TiO 2 pigment because it promotes the anatase-to-rutile phase transition of TiO 2 at lower temperatures (vs. Al3+). However, research on the impact of Mg2+ concentration on TiO 2 phase transition is scarce, and the defect structures are still unknown. In this study, the effect of Mg2+ doping concentration on TiO 2 phase transition was investigated, and the defect structures of Mg2+ doped TiO 2 were proposed. Over 96% conversion of anatase to rutile was achieved with 1.48% Mg doping at 875 °C (vs. Al3+, 1050 °C) for 1 h. By using the Rietveld method, two defect structures—interstitial Mg2+ (Mg int) and substitute Mg2+ (Mg sub)—were quantified. A correlation between the defect structures and the effect on phase transition was established. At low Mg doping level (<1%), the Mg int dominates and weakly promotes the phase transition; At high Mg doping level (>1%), the Mg sub dominates and strongly promotes the phase transition. Additionally, a possible mechanism for the formation of defect structures and how that affects phase transition was proposed. The present results may provide insights into TiO 2 pigment production and modulation of TiO 2 defects for phase transition control and other applications. • 96% conversion of anatase to rutile was achieved at 875 °C (1050 °C in industry). • The two defect structures of Mg2+ doped TiO 2 —interstitial Mg2+ and substitute Mg2+—were quantified by Rietveld method. • The correlation between defect structures and phase transition is established. • The possible mechanism for the formation of defect structures and how that affects phase transition was proposed. [ABSTRACT FROM AUTHOR]