Phase stability of the thermal barrier deposits made from yttria-partially-stabilized zirconia (Y-PSZ) is a requirement for extended service lifetime. The response of Y-PSZ plasma-sprayed deposits to annealing at 1000 °C, 1200 °C, and 1400 °C with times from 1 to 1000 hours has been evaluated using Rietveld analysis of neutron diffraction data. Results show that yttria concentration of the as-sprayed tetragonal zirconia component generally decreased with increasing annealing temperature and time. As the yttria content in the tetragonal phase approached a limiting concentration, the tetragonal phase transformed into monoclinic phase on cooling. An increase in monoclinic phase content was clearly observable after annealing 24 hours at 1400 °C and was nearly 35 % after 100 hours at 1400 °C. A similar trend was observed at 1200 °C for longer annealing times, with monoclinic phase formation beginning after 400 hours. At 1000 °C experimental times were not sufficient for monoclinic phase to form although a decrease in the yttria concentration in the tetragonal phase was observed. Keywords: neutron scattering, yttria-stabilized zirconia, phase composition, Rietveld analysis

This paper describes the technique of anisotropic multiple small-angle neutron scattering (MSANS). Anisotropic MSANS, when combined with anisotropic Porod scattering, electron microscopy, and measurements of elastic modulus and density, has made possible the determination of the porosities, surface areas, mean opening dimensions, mean diameters, and approximate orientation distributions, of the intra-splat cracks and interlamellar pores, as well as the porosity, surface area, and mean diameter, of the globular pores. The changes in these parameters, as a function of annealing, are studied. Paper includes a German-language abstract.

This paper presents novel results of a series of experiments intended to study the role of the size of the feedstock powder on the microstructure of the deposits. For this purpose, Metco and the feedstock powder, yttria-stabilized (8% wt) zirconia, with number-weighted mean particle sizes of 32, 47, 56, and, 88 micrometer, are used. Small-angle neutron scattering and multiple small-angle neutron scattering (MSANS) methods are applied to determine the microstructure of the four deposits. Companion indentation measurements are performed to determine the elastic moduli of the deposits. The paper also discusses the MSANS 3-void model in relation to the anisotropic elastic properties. Paper includes a German-language abstract.