| Popis: |
There is increasing interest in IR window materials with transmissionn limits of > 5 μm, increased mechanical toughness, and higher temperature capability. ZrO 2 , which transmits to 7-8 μm is a possible candidate material for such needs. While its IR cut-off is at somewhat shorter wavelengths than other candidates (e.g. Y 2 0 3 with a cut-off of - 9 μm), ZrO 2 offers the potential of significant toughening via a two phase, i.e. partially stabilized, structure. Such structures, and the relevant toughening mechanisms are reviewed, and the resultant mechanical properties discussed, particularly for the Zr0 2 -Y20 3 system. For example, some materials in this system can give strengths of about 1.5 GPa (200,000 psi) at 22°C and nearly 0.7 GPa (100,000 psi) at 1500°C for laboratory test specimens. Preliminary optical measurements, including some outlining optical scattering effects of the second (precipitate) phase, required for mechanical toughening are presented. These suggest that useful transmission in the range of interest is achievable with these toughened ZrO 2 materials. |
