Microwave Complex Permittivity of Yttria-Stabilized Zirconia

The complex permittivity of 8-mol yttria-stabilized zirconia (8-YSZ) in powder and sintered (i.e., solid) forms were measured from 32 to 40 GHz using a circular waveguide probe. This probe is suitable for measuring both the powder and solid forms of materials. Comparative completely filled rectangular waveguide measurements of the powder were performed at three frequency bands to verify these results and also to extend the measured complex permittivity estimation frequency range. The results indicated good agreement between the two different measurement techniques. The complex permittivity of the 8-YSZ powder was measured to be
$(\epsilon _{r} = 2.45 - j0.04)$
. Conductor-backed solid 8-YSZ, representative of an in-service ceramic coating, was also measured using the circular waveguide probe. Complex permittivity was measured to be significantly higher
$(\epsilon _{r} = 29.28 - j0.07)$
when the 8-YSZ was sintered into a solid form. This was attributed to densification and other effects occurring during the sintering process.