SEGREGATION IN SINGLE-CRYSTAL FULLY STABILIZED YTTRIA-ZIRCONIA

X-rag photoelectron spectroscopy (XPS) has been used to study surface segregation in 9.5 mol% single-crystal Y2O3-ZrO2 which has been subjected to air anneals at temperatures ranging from 900 degrees to 1500 degrees C. The kinetics of segregation reveal an enrichment of Y, Si, Na, and Fe at short times; however, at longer times surface equilibrium is reached. The heats of segregation for Y, Si, Na and Fe, determined from Arrhenius plots, were 9.3 +/- 3.0, 59.0 +/- 7.0, -23.5 +/- 11.5, -18.0 +/- 6.0 kJ/mol, respectively. XPS analysis of the equilibrium states at all temperatures revealed a distinct surface layer which, given the positive heats of segregation for Si and Y, is quite stable.