Philippe I just did a search on Si3N4 zirconium properties.
I came up with the above websites that may pertain to what your
looking for. There are some pay sites for technical information. The
best thing to do is talk to vendors who supply the ceramics. They
will have material data sheets.
Ultra High Temperature Ceramics Assessed For Reusable Propulsion
Applications: An assessment of zirconium diboride based ultra high
temperature ceramics (UHTC) for a reusable propulsion application was
completed. Silicon nitride was used as a reference material. The study
determined that the UHTC have oxidation rates 3 to 4 orders of
magnitude greater than Si3N4, and thermal shock resistance
significantly less than Si3N4. Thus zirconium diboride and similar
hafnium diboride UHTCs are not suitable for reusable propulsion
applications. Studies are continuing to improve the oxidation
resistance of UHTC materials. (Stan Levine, Beth Opila (5160), Mike
Halbig, Doug Kiser, Jay Singh, and Jon Salem, (5920))
Found this on one of the links in my search right after my last post.
I am sure there is more but this is simple enough to search for:).