Microstructure of Nanocrystalline Yttria‐Doped Zirconia Thin Films Obtained by Sol–Gel Processing

Nano‐ and microcrystalline yttria‐stabilized zirconia (YSZ) thin films with a dopant concentration of 8.3±0.3 mol% Y 2 O 3 were prepared with a variation in grain size by two orders of magnitude. A sol–gel‐based method with consecutive rapid thermal annealing was applied to fabricate YSZ films, resulting in about 400 nm YSZ on sapphire substrates. The average grain sizes were varied between 5 nm and 0.5 μm by heat treatment in the temperature range of 650°–1350°C for 24 h. High‐resolution (HRTEM) and conventional transmission electron microscopy analyses confirmed specimens—irrespective of the thermal treatment—consisting of cubic ( c ‐)ZrO 2 grains with nanoscaled tetragonal precipitates coherently embedded in the cubic matrix. Energy‐dispersive X‐ray spectroscopy and HRTEM on a large number of specimens yielded a homogeneous yttria concentration within the grains and at the grain boundaries with the absence of impurities, i.e. silica at the grain boundaries.