Room‐temperature plastic deformation of single crystals of high‐purity β‐silicon nitride investigated by micropillar compression

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Abstract
The room‐temperature plastic deformation behavior of single crystals of high‐purity β‐silicon nitride has been investigated by micropillar compression tests as a function of loading‐axis orientation and specimen size. Prism < c > slip ({010}[0001] slip) is identified to be the only operative slip system under uniaxial compression at room temperature. The critical resolved shear stress (CRSS) value for prism < c > slip does not depend much on the specimen size and loading‐axis orientation, with the average CRSS value of 1.66 ± 0.22 GPa. The [0001] dislocations on the prism slip planes exhibit a strong tendency to align along their screw orientation, indicating the existence of a high Peierls barrier for the [0001] dislocation in the screw orientation. The generalized stacking fault energy calculations by first‐principles density functional theory indicate that the [0001] dislocations prefer to glide as undissociated dislocations on the prism slip plane with the largest interplanar spacing, where the large empty channels (imaged as regular hexagons in the [0001] projection) are not cut. The values of fracture toughness KIC are evaluated to be 2.0–2.3 MPa·m1/2 without apparent orientation dependence by single‐cantilever bend tests of chevron‐notched single‐crystal specimens. In addition, grain boundary sliding is found to occur at a relatively low shear stress of about 0.9–3.3 GPa during compression tests on micropillar specimens unintentionally containing a grain boundary.
Funding Information
  • Japan Society for the Promotion of Science (JP19H00824, JP22H00262, JP23K17338, JP25H00801)
  • Ministry of Education, Culture, Sports, Science and Technology (JPMXP0112101000)
  • Kyoto University Foundation
  • Kyoto University

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