Flash sintering of HfO ₂ at 1050°C in a bilayer with 8YSZ

Abstract Some materials are difficult to sinter by flash method, as they require both extremely high temperatures and intense electric fields. For such materials, a common strategy is to mix them with a powder of an easily flashable material that acts as a catalyst. Here we demonstrate that HfO 2 , which is difficult to flash even at very high fields and very high furnace temperatures, can be sintered by flash in a bilayer configuration with yttria‐stabilized zirconia. Flash in zirconia layer propagated into the hafnia layer, made from monoclinic powders, causing it to flash and sinter at 800°C. The HfO 2 layer sintered to a relative density of ∼95%, with a grain size of 470 nm. Dielectric constant of the flash‐sintered HfO 2 was comparable to conventionally sintered and FAST/spark plasma‐sintered–processed specimens. The present method offers a viable route to overcome the long‐standing challenge of densifying high‐resistance refractory ceramics without the use of sintering aids.