Transformation Toughening by Fracture-Induced Amorphization in Nanopolycrystalline Stishovite

Abstract

Nanopolycrystalline stishovite was fabricated under high pressure and temperature using Kawai-type apparatus. This material is the hardest oxide as well as one of the toughest ceramics with fracture toughness of about 12 MPa m^1/2. We performed X-ray absorption spectroscopy using synchrotron radiation, bending tests using micro-cantilever specimens fabricated by focused ion beam technique, and first-principles calculations for this material. Using the obtained results, we demonstrated that this material is toughened by transformation toughening mechanism by fracture-induced amorphization of stishovite. This toughening mechanism can be a platform to produce new structural materials.