X-RAY PHOTOELECTRON SPECTROSCOPIC STUDIES ON YTTRIA-STABILIZED ZIRCONIA AND ITS SURFACE TRANSFORMATIONS

Yttria-stabilized zirconia is an important structural ceramic with excellent mechanical properties. A stress-induced phase transformation from tetragonal to monoclinic crystal structure occurs in this material resulting in high strength with high fracture toughness and improved wear resistance. Surfaces and grain boundaries of yttria-stabilized zirconia were studied using X-ray photoelectron spectroscopy. Segregation of yttrium was observed at the surface as well as at the grain boundaries. The binding energies of zirconium and yttrium core levels in tetragonal yttria-stabilized zirconia were different from their values in standard zirconia and yttria respectively, indicating chemical shifts. Valence bands and Auger parameters were determined for the various phases of zirconia. Characteristic differences were observed for the monoclinic and the tetragonal phases owing to their different oxygen coordination. The results were used to monitor changes at the surface of yttria-stabilized zirconia subjected to various treatments.