Fracture Strength of Single-Crystal Silicon Carbide Microspecimens at 24 $^{\circ}\hbox{C}$ and 1000 $^{\circ}\hbox{C}$

Abstract

Three shapes of silicon carbide tensile specimens were tested-curved with a low stress-concentration factor and straight with a circular hole or an elliptical hole. The nominal thickness was 125 µm with a net section that is 100-µm wide; the overall length of these microspecimens was 3.1 mm. They were fabricated by an improved version of deep reactive ion etching, which produced specimens with smooth sidewalls and cross sections having a slightly trapezoidal shape that was exaggerated inside the holes. The novel test setup used a vertical load train extending into a resistance furnace. The specimens had wedge-shaped ends which fit into ceramic grips. The fixed grip was mounted on a ceramic post, and the movable grip was connected to a load cell and actuator outside the furnace with a ceramic-encased nichrome wire. The same arrangement was used for tests at 24 • C and at 1000 • C. The strengths of the curved specimens for two batches of material (made with slightly different processes) were 0.66 ± 0.12 and 0.45 ± 0.20 GPa, respectively, at 24 • C with identical values at 1000 • C. The fracture strengths of the circular-hole and elliptical-hole specimens (computed from the stress-concentration factors and measured loads at failure) were approximately 1.2 GPa with slight decreases at the higher temperature. Fractographic examinations showed failures initiating on the surface-primarily at corners. Weibull predictions of fracture strengths for the hole specimens based on the properties of the curved specimens were reasonably effective for the circular holes but not for the elliptical holes.[2007-0057]

An initial consideration of silicon carbide devices in pressure-packages

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A Multiphysics Modeling and Experimental Analysis of Pressure Contacts in Power Electronics Applications

“…It should be noted that the yield stress of SiC is 21 GPa [23]. According to Sharp et al [24], the fracture strength of smooth SiC of any shaped specimen is in the range of 0.5 -1.5 GPa. Additionally in the experiment we haven't observed any crack in the chip for both contact pad materials.…”

High-Temperature Fracture Strength of a CVD-SiC Coating Layer for TRISO Nuclear Fuel Particles by a Micro-Tensile Test

“…Various methods for the micro-tensile testing of SiC coatings have been proposed, such as the specimen end inserted in holder, a specimen fixed onto the holder using adhesives, a grip holder to grip a specimen, and a holed specimen loaded on a holder using pins. [16][17][18][19][20] The present study developed a new grip method by which the specimen was fixed onto small ceramic holders and held by a ceramic pin. A thin and brittle SiC tensile specimen was used for the high-temperature micro-tensile test using an Instron 8848 micro-tester (Micro Force System, Instron, USA).…”