, Volume 10, Issue 3, pp 497-501

Thermal spray yttria-stabilized zirconia phase changes during annealing

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Abstract

Phase stability of 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, 1200, and 1400 °C with times from 1 to 1000 h has been evaluated using the Rietveld analysis of neutron diffraction data. Results show that the 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, about 3.5 mol.% of YO1,5, the tetragonal phase transformed into monoclinic phase on cooling. An increase in monoclinic phase content was clearly observed after annealing for 24 h at 1400 °C and was nearly 35% after 100 h at 1400 °C. A similar trend was observed at 1200 °C for longer annealing times, with monoclinic phase formation beginning after 400 h. 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.