Abstract
The microstructures of as-sprayed and thermally-cycled freestanding and on-substrate deposits of yttria-stabilized zirconia were studied using small-angle neutron scattering (SANS). The SANS analysis allows the interlamellar pores and the intralamellar cracks, which are the two dominant void systems in the microstructure, to be characterized separately. Whereas up to 20% of the void surface area in the as-sprayed deposits was found to be in the cracks, the thermally-cycled deposits contained only a negligible quantity of cracks. At the same time, changes in the pore surface areas between the lamellae (i.e., the interlamellar pores) were much smaller. As a result, the microstructure of the thermally-cycled deposits was much more anisotropic than the microstructure of the as-sprayed deposits. Varying the cooling and the heating rates did not significantly change the microstructure but varying the total time that the deposits were at high temperature did affect the evolution of the surface area. The presence or absence of a bond coat and substrate also did not measurably influence the results.
