Rapid rate sintering of nanocrystalline indium tin oxide ceramics: particle size effect

The nanocrystalline indium tin oxide (ITO) powders with different particle size were prepared using a coprecipitation process and the sintering characteristics of the powders at different heating rate were examined. Decrease of particle size in nano-sized powder regime promoted the densification in normal rate sintering as temperature increased, while this retarded severely the densification at high temperature in rapid rate sintering. It is explained due to the differential densification, that is, the outmost region of the sample is well densified, while many large pores are observed inside of the densified ring. The differential densification may easily occur in the sample sintered at high temperature with small particles in rapid rate sintering, because smaller particle size has higher densification rate and higher sintering temperature in rapid rate sintering accompanies higher thermal gradient between the surface and center of a sample.