Preparation of nanostructured TiO 2 ceramics by spark plasma sintering Young Il Lee, Jong-Heun Lee * , Seong-Hyeon Hong, Doh-Yeon Kim School of Materials Science and Engineering, Center for Microstructure Science of Materials, Seoul National University, Seoul 151-744, South Korea Received 17 July 2002; received in revised form 5 March 2003; accepted 17 March 2003 Abstract The effect of spark plasma sintering (SPS) on the densification of TiO 2 ceramics was investigated using a nanocrystalline TiO 2 powder. A fully-dense TiO 2 specimen with an average grain size of 200 nm was obtained by SPS at 700 8C for 1 h. In contrast, a theoretical density specimen could only be obtained using conventional sintering above 900 8C for 1 h with an average grain size of 1–2 mm. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: A. Ceramics; A. Nanostructure; D. Microstructure 1. Introduction There has been an increasing interest in nanocrystalline TiO 2 both in powder and ceramics forms. The highly active surface of a nanocrystalline TiO 2 powder plays a key role in its catalytic [1], photo- catalytic [1], and gas-sensing properties [2]. Moreover, a nanocrystalline powder can provide fast densification kinetics with a lower sintering temperature [3]. A nanostructured TiO 2 ceramic is also of great importance in the low-temperature creep [4] and electrical properties of TiO 2 . For example, it has been reported that the specific grain boundary resistivity of TiO 2 significantly decreased with decreasing grain size [5]. However, preparing a fully-dense fine-grained TiO 2 specimen is difficult because the grains grow rapidly at the later stages of sintering [6,7]. The sintered microstructure is largely determined by the powder characteristics and the initial microstructure; hence, many attempts have been made to prepare an agglomeration free, well compacting nanosized powder in order to fabricate fully-dense nanostructured ceramics [8]. Other approaches are the employment of a new sintering process including Materials Research Bulletin 38 (2003) 925–930 * Corresponding author. Tel.: þ82-2-880-6891; fax: þ82-2-884-1413. E-mail address: jongheun@gong.snu.ac.kr (J.-H. Lee). 0025-5408/03/$ – see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0025-5408(03)00084-9