X-ray photoelectron spectroscopic studies of Al3þ stabilized t-ZrO2 of nanoparticles

Al3þ stabilized tetragonal (t)-ZrO2 of nanoparticles is studied with X-ray photoelectron spectroscopy (XPS) as a function of the Al3þ concentration. The samples, with 2–15 mol% Al3þ additives, are prepared by co-hydrolysis of the two types of the metal cations in an amorphous precursor of oxyhydroxyl Zr1 2xAl2xO(OH)2 2x aH2O gel. Substantially stabile t-ZrO2 occurs with the Al3þ additives on a reconstructive thermal decomposition of gel by heating at 500 8C in air. The Al3þ additive inhibits average t-ZrO2 crystallite size to be as small as 6–8 nm (9 nm otherwise in virgin t-ZrO2) depending on the Al3þ concentration. As analyzed with X-ray diffraction, no independent Al2O3 crystallizes, confirming formation of a perfect Al3þ:ZrO2 solid solution under these conditions. Six distinct XPS bandgroups lie, in the 0–600 eV range of the binding energy, in excitations of 2p, 2s, 4p, 3d, or 3p core electrons in Al3þ and Zr4þ cations and in 1s excitation in O2 anions in Al3þ:t-ZrO2 solid solution. Weak satellite 3d5/2 and 3d3/2 bands occur at lowered energies (8–10 eV) of the main bands in trace of part of the metal cations present in the lower Zrqþ, q 3, oxidation states. # 2003 Elsevier B.V. All rights reserved