Fracture toughness measurements of YBa2Cu3O<i>x</i> single crystals

Abstract

We report fracture toughness measurements on single crystals of YBa2Cu3Ox, the phase responsible for superconductivity above liquid-nitrogen temperatures. Indentation crack length measurements on the (010) orthorhombic crystal growth faces revealed the (100) and (001) planes as preferred fracture planes. The toughness of these planes is Kc=1.1±0.3 MPa m1/2, and the hardness H=8.7±2.4 GPa. The observed growth of both radial and lateral cracks in ambient air suggests that these crystals are susceptible to moisture-enhanced nonequilibrium crack propagation.