Effects of interparticle neck size on initiation of selective laser flash sintering of 8‐YSZ

The influence of the interparticle neck radius to particle size ratio (X/R) on the laser energy required to initiate selective laser flash sintering (SLFS) in 8% yttria‐stabilized zirconia (8‐YSZ) is investigated. The interparticle neck radius ratio (X/R) is varied by pre‐sintering powder compacts at temperatures ranging from 850°C to 1250°C to produce compacts with calculated X/R = 0–0.62. Experiments show that the onset laser energy to initiate SLFS initially decreases with X/R until X/R = 0.066, when the onset laser energy reaches a minimum. As X/R increases beyond 0.066, the onset laser energy increases. Finite element modeling is used to calculate the local current density and temperature in the neck region when SLFS initiates. When interparticle necks are small, the current density and Joule heating are substantially elevated near necks, resulting in a relatively low laser onset energy required for incipient current flow. When the interparticle neck size is increased, the laser onset energy for incipient current flow is increased because Joule heating in the neck region is lower, but locally high current density spreads into the interior of the particles more quickly with larger necks. These results provide valuable insights into the mechanisms responsible for the initiation of both SLFS and furnace‐based flash sintering.