Deformation behaviors and fracture strength of β$\ubeta$‐Si₃N₄ single crystals

Abstract

In this study, the yield stress and fracture strength of β$\ubeta$‐Si3N4 single crystals were directly measured by bending tests of microcantilever beam specimens that were prepared by a focused ion beam method. The β$\ubeta$‐Si3N4 single crystals were plastically deformed at room temperature under high bending stress, and the yield stress depended on the crystal orientation. Transmission electron microscopy observation of the specimens after bending tests indicates that the plastic deformation resulted from dislocations in the primary slip system false{10true1¯0false}$\{ 10\bar{1}0\} $<0001>, and the critical resolved shear stress of this slip system determined from the yield stress was 1.34 GPa. The fracture strength of β$\ubeta$‐Si3N4 single crystals ranged approximately up to 20 GPa, depending on the crystal orientation as with the yield stress. The fracture behavior of β$\ubeta$‐Si3N4 single crystals was discussed in terms of the accumulation of dislocations.

Micro‐scale mechanical properties of surface layer in ion‐exchanged glass

“…The microcantilever bending test is a powerful technique that can measure mechanical properties at a micro‐scale under tensile stress 12–21 . A load is applied at the tip of a microcantilever beam specimen to generate the bending stress on the top surface of the specimen.…”

“…The microcantilever bending test is a powerful technique that can measure mechanical properties at a micro-scale under tensile stress. [12][13][14][15][16][17][18][19][20][21] A load is applied at the tip of a microcantilever beam specimen to generate the bending stress on the top surface of the specimen. This method has been employed for investigating micro-scale mechanical performance of various inorganic materials including silicon nitride, [12][13][14] silicon carbide, 15 silicon, 16 zirconia, 17,18 alumina, 19 hydroxyapatite, 20 and high-entropy carbide.…”

“…[12][13][14][15][16][17][18][19][20][21] A load is applied at the tip of a microcantilever beam specimen to generate the bending stress on the top surface of the specimen. This method has been employed for investigating micro-scale mechanical performance of various inorganic materials including silicon nitride, [12][13][14] silicon carbide, 15 silicon, 16 zirconia, 17,18 alumina, 19 hydroxyapatite, 20 and high-entropy carbide. 21 The specimen thickness is typically two to three microns, while the case depth or the depth of the surface compression of ion-exchanged glass is usually several to several ten microns.…”

Effect of initial phase composition on the phase composition, microstructure, and mechanical properties of Si3N4 ceramics

“…The α‐Si 3 N 4 exhibits high sintering activity and high hardiness and transforms into the β‐Si 3 N 4 during sintering. Comparing to the α‐Si 3 N 4 , the β‐Si 3 N 4 exhibits lower hardness and rod‐like morphology, 4–6 which usually forms tough interlocking microstructures during sintering 6–10 . However, it is difficult to balance the high hardness of α‐Si 3 N 4 and the high fracture toughness of β‐Si 3 N 4 in Si 3 N 4 ceramics.…”