Phase composition and stability of nanostructured 4.7 wt.% yttria-stabilized zirconia coatings deposited by atmospheric plasma spraying

Phase composition and stability of plasma-sprayed nanostructured 4.7 Wt.% Y2O3-stabilized zirconia coatings were investigated by using X-ray diffraction (XRD) and Raman spectroscopy. The nanostructured as-sprayed coatings consisted of a nontransformable tetragonal phase (T' phase) and an orthorhombic phase. The T' phase decomposed into the low-yttria and high-yttria tetragonal phases when the annealing temperature was above 1200 degrees C. The orthorhombic phase observed during annealing resulted from the fast densification of the as-sprayed coating. It acted as an intermediate phase of the transformation of the low-yttria tetragonal to a monoclinic phase during cooling. The orthorhombic phase quickly decreased when the transformation spontaneously occurred due to the grain size being larger than the critical size. (c) 2005 Elsevier B.V All rights reserved.