The sintering of polycrystalline ceramics with a homogenous microstructure and a fine grain size is of great inportance, since the mechanical properties of fine-grain ceramics, including their fracture toughness and bending strength, are significantly enhanced with decreasing particle size. However, the fabrication of fine-grain ceramics is challenging due to the competition between densification and grain growth during sintering. 
In this work, a fine-grain 3 mol% yttria-stabilized zirconia (3YSZ) ceramic was successfully prepared by a novel two-stage flash sintering method. This method used the current-surge stage (II stage, < 2 s) of flash sintering to obtain a relatively high-density ceramic with limited grain growth, followed by further densification in a current-control stage (III stage) with low-current-density stimulation. The dense 3YSZ ceramics were obtained with an average particle size of 170±16 nm, a relative density of 95.7%, and a hardness of 1270Hv.