Band gap tuning of oxygen vacancy-induced Al2O3-TiO2 ceramics processed by spark plasma sintering

Abstract

Optical and photocatalytic applications of Al 2 O 3 and TiO 2 ceramics are limited, especially under visible light, due to their wide bandgap; so, this parameter plays an important and even decisive role in these applications. In the present study, Al 2 O 3 -TiO 2 ball milled powders were sintered by spark plasma sintering (SPS) at 1573 K. The products were characterized using XRD, SEM, UV-Vis and electrochemical methods. The results indicated effective improvement in the light absorbing capability of the composites (up to 95%) under visible light and the decrease of the band gap down to 2.2 eV owing to the increase of oxygen vacancies, which was, in turn, due to the reduced atmosphere of the sintering process. In addition, formation of a new phase (Al 2 TiO 5 ) during sintering greatly affected the absorption of Al 2 O 3 -TiO 2 composites in the visible light region due to the increase in the fraction of the charge carrier separation centers. Photo-luminescence spectroscopy also showed that tialite formation could be effective in improving the charge separation efficiency.