Near‐surface plastic deformation in polycrystalline SrTiO${}_3$ via room‐temperature cyclic Brinell indentation

Dislocations are being used to tune versatile mechanical and functional properties in oxides with most current studies focusing on single crystals. For potentially wider applications, polycrystalline ceramics are of concern, provided that dislocations can be successfully introduced. However, in addition to preexisting pores and flaws, a major barrier for bulk plastic deformation of polycrystalline ceramics lies in the grain boundaries (GBs), which can lead to dislocation pile-up and cracking at the GBs due to the lack of sufficient independent slip systems in ceramics at room temperature. Here, we use the cyclic Brinell indentation method to circumvent the bulk deformation and focus on near-surface regions to investigate the plastic deformation of polycrystalline SrTiO${}_3$ at room temperature. Dislocation etch-pit analysis suggests that plastic deformation can be initiated within the grains, at the GBs, and from the GB triple junction pores. The deformability of the individual grains is found to be dependent on the number of cycles, as also independently evidenced on single-crystal SrTiO${}_3$ with representative surface orientations (001), (011), and (111). ... mehrWe also identify a grain-size-dependent plastic deformation.