Rapid synthesis of zirconium titanate by reactive flash sintering

Abstract Zirconium titanate (ZrTiO 4 ) is a technologically important ceramic that is difficult to synthesize by conventional sintering, typically requiring several hours of heat treatment at temperatures around 1500°C. It undergoes a sluggish order–disorder transition near 1125°C. At low temperatures, Zr 4+ and Ti 4+ ions occupy ordered lattice sites, whereas heating above 1200°C causes these cations to exchange positions randomly, transforming the material into a disordered, symmetric phase. Although the disordered phase is stable above 1200°C, achieving homogeneity at lower temperatures requires prolonged or repeated annealing treatments. Here, we demonstrate that zirconium titanate can be rapidly synthesized by reactive flash sintering (RFS), in which mixed oxide powders simultaneously densify and react to form a single phase within 30 s at a furnace temperature of 800°C. Experiments were carried out at nominal current densities of 60, 100, and 140 mA/mm 2 . Unlike conventional flash sintering, which typically occurs in stage II near the flash onset, sintering in this case initiated in stage III, followed by the formation of the ZrTiO 4 phase. This phase formation was accompanied by a measurable volume expansion. By carefully controlling furnace temperature, current density, and hold time, two distinct phases—ZrTiO 4 and Zr 5 Ti 7 O 24 —were successfully stabilized. In summary, dense ZrTiO 4 with ∼95% relative density and a hardness of ∼11 GPa was obtained by optimizing the electrical parameters. Rapid cooling of the specimen immediately after flash termination effectively suppressed the order–disorder transition. A small amount of residual TiO 2 remained due to the use of an equivolumetric initial powder mixture.