Two-step sintering (TSS) concept was adopted in the consolidation of 3 mol% yttria doped zirconia nanopowder. Partially densified bodies with 87%
theoretical density (TD) were firstly prepared using high-pressure spark plasma sintering (SPS) technique and followed by second-step pressureless
sintering. The samples achieved only 96% TD final density after 30 h soaking. It was found that the densification process was impeded by dynamic
pore coalescence with a pore growth factor of 10. The phenomenon was explained by the coalescence of interconnected small pores generated
by differential sintering of nanoceramic green compacts. Such pore coalescence was accompanied with particle movement, which resulted in
sintering state deviating from the frozen state. Present results indicated that the active range for particle rearrangement was greatly extended during
nanoceramic sintering and the efficiency of TSS approach was greatly dependent on the homogeneity of green bodies.