Making nanostructured ceramics from micrometer-sized powders via grain refinement during SPS sintering

In this paper, we have demonstrated that dense bulk nanostructured ceramics can be synthesized from micrometer-sized powders by using an electrical field-activated sintering process. A dense Pb(Mg_1/3Nb _2/3)O₃-PbTiO₃ ceramic with grain sizes of 20-100 nm was obtained from the starting powder of 1 to 10 μm. Structural and property analysis confirmed that the entire specimen is composed of nano-sized grains. The significant microstructural refining is attributed to a pulsed electric field-induced thermo-mechanical fatigue process, which in situ "shattered" the large particles into nano-sized grains during sintering. An advantage of this technique over the previous ones is that it avoids the usage of ultrafine nanometer-sized powders, which are difficult to process and mass produce in an economic and consistent way. In principle, the process demonstrated here can be applied to other material systems.