The effect of atmosphere on the flash-sintering of nanoscale titania ceramics

Flash-sintering is a promising approach for the ultra-rapid densification of ceramics at low furnace temperatures under an applied electric field. Here we have studied the effect of atmosphere on the flash-sintering of titania (TiO2) nanopowders under an applied electric field of 400 V.cm(-1), and find a dramatic reduction in the flash-onset furnace temperature (T-F), from 648 degrees C in air to 239 degrees C in argon (Ar). The reduced T-F is close to the TiO2 Debye-temperature limit. This is attributed to a combination of nanocrystalline nature of the TiO2 powder and the O-2-lean Ar atmosphere, resulting in enhanced electrical-conductivity characteristics. The reduced T-F also results in finer, uniform average grain sizes (360 nm to 190 nm) and lower, uniform porosity (0.5% to 1.4%), going from the anode to the cathode. In contrast, in air the corresponding average-grain-size range is 9.6 mu m to 1.3 mu m and the porosity range is 1.9% to 3.3%. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The atmosphere significantly affects the flash-sintering process, with the use of argon resulting in a dramatic reduction in the flash-onset furnace temperature for titania nanopowders. This leads to finer, more uniform grain sizes and lower, uniform porosity in the ceramics.