Low-Temperature Fracture Strength of MgB2 Bulk Processed by Spark Plasma Sintering

Mechanical properties of a high packing ratio MgB
₂
bulk sample processed by spark plasma sintering (SPS) were evaluated at 77 K through bending tests for specimens cut from the bulk sample. The effects of the packing ratio and temperature on the fracture strength of MgB
₂
bulk are discussed. The fracture strength at 77 K of the MgB
₂
bulk processed by SPS was higher than that at room temperature. The packing ratio of the MgB
₂
bulk processed by SPS was higher than those of other MgB
₂
bulks processed by sintering under the ambient pressure and hot isostatic pressing. The fracture strength was improved by increasing the packing ratio. The fracture strength at a very low temperature was estimated from the bending test results at 77 K and room temperature. The fracture strength at 20 K of the MgB
₂
bulk processed by SPS was estimated to be around 425 MPa.