Grain-size effects on the hardness of nanograin BaTiO3 ceramics

Abstract

Dense nanocrystalline BaTiO3 (BT) ceramics with grain size (GS) 50 nm were successfully prepared by spark plasma sintering (SPS) method. The nanoindentation experiment was used to test the hardness of different GS BT ceramics. It was found that the hardness of 50 nm nanograin BT ceramics increased 82% than that of 1.2 μm BT ceramics fabricated by conventional sintering (CS) process. Dislocation pinning resulting from the increase of grain boundary by ultrafine GS are believed to be the dominant factor in raising strength. Restriction on dislocation generation and mobility due to the domain wall motion and sliding imposed by ultrafine GS are expected to be exceptionally important. At the same time, the large stress in nanograin BT ceramics may also play a role in producing high strength. These differences of the hardness behavior between BT ceramics are attributed to the variation of the resultant microstructure, especially the GS of the ceramics.