Stabilization of tetragonal ZrO2 with Al2O3 in reactive magnetron sputtered thin films

Thin-film mixtures of zirconia and alumina 1–2 μm in thickness were produced by sputtering composite targets of zirconium and aluminum metals and reacting the metal vapor with oxygen. X-ray and selected area electron diffraction indicated that the films deposited at room temperature were amorphous. Rutherford backscattering measurements indicated that the films were stoichiometric. Annealing at 1000 °C for 48 h produced ordering of the zirconia phase, and the zirconia crystal structure was strongly dependent upon the relative amounts of zirconium and aluminum. Pure zirconia was monoclinic as was a mixture with a zirconium-to-aluminum atom ratio of 0.76:0.24. For the mixture with a zirconium-to-aluminum atom ratio of 0.52:0.48 the tetragonal phase of zirconia was observed with only a trace of the monoclinic phase. The alumina phase apparently orders much more slowly than zirconia, and no alumina diffraction peaks were observed in any of these mixtures with zirconium-to-aluminum atom ratios down to 0.52:0.48.