We studied the influence of the annealing temperature on the atomic structure of yttria-stabilized tetragonal zirconia (YSZ) which was deposited as a 300 mum thick thermal barrier coating (TBC) on nickel superalloy substrates by plasma spraying. To obtain neutron powder diffraction patterns of the barrier coatings we used an experimental technique where the sample is randomly rotated in the neutron beam. The time-averaged neutron diffraction pattern was then analyzed using the Rietveld refinement technique without any need for corrections. This allowed the comparison of the average crystals structures from bulk tetragonal samples obtained via common ceramic routes and those of micrometer thick films deposited on substrates using plasma spray or other nonequilibrium techniques.