Silver catalytic effect on flash sintering of ceramics

We investigated the use of metallic silver as a catalyst for flash sintering on hydroxyapatite/zirconia (HZ) composites. Adding 3 wt.% of silver to the ceramic powder reduced the flash onset temperature (from 1084 °C to 925 °C) and also the electric field (from 300 V.cm−1 to 150 V.cm−1) used in the process. We attribute this behaviour to the formation of a silver percolation path that acts as a heat source, accelerating the thermal runaway. As a result, both the flash temperature and the required electric field were reduced. Furthermore, the results suggest that the temperatures along the percolation paths are high enough to reach the boiling point of silver, forming a gaseous phase that leaves the sample.