Mechanical evaluation of yttria

A method is described to make multiple measurements of the strength of a single hemispherical ceramic dome with a ring-on-ring flexure test of disklike sections removed from the dome by a core drill. Preliminary results show that dome cores exhibit lower strength than flat disks, because the domes have larger critical surface flaws than those present on disks. Careful attention to polishing of domes is required to realize maximum strength from the domes. The fracture toughness of optical quality yttria disks and hemispherical domes was found to be approximately 0.7 MPa'I m.