Laser-induced solid solution of the binary nanoparticle system Al2O3-ZrO2

Nanoparticles of the system Al2O3-ZrO2 were produced by simultaneous vaporization of Al2O3 and ZrO2 microparticles with the radiation of a 1000 W Nd:YAG-laser and subsequent condensation of the induced vapor in a controlled atmosphere. The nanoparticles were investigated by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), electron diffraction (ED) and X-ray diffraction (XRD). The analysis of the as-prepared nanoparticles showed that the nanoparticles are single crystals having spherical shape with a median particle diameter of 14 nm. EDX and high resolution TEM investigations on single crystals showed the existence of a so lid solution of the binary system Al2O3-ZrO2, which is formed during the particle nucleation and rapid quenching. XRD measurements of the powder reveal the presence of ZrO2 in the tetragonal structure (t-ZrO2) and of species of tetragonal structure with decreased lattice parameters compared to t-ZrO2. The last can be attributed to a metastable solid solution of the type Zr(1-x)AlxO(2-x/2) (0 < x < 1), as also confirmed by ED measurements. When the powders were thermally treated at a temperature T-s = 700 degrees C, the diffraction patterns assigned to the solid solution vanished in the XRD and ED spectra due to decomposition of the particles as supported by EDX and high resolution TEM measurements on single nanoparticles. At T-s greater than or equal to 1200 degrees C, enhanced grain growth of the particles was observed by TEM. XRD-investigation showed that the particles started transforming into their equilibrium phase assembly, m-ZrO2 and alpha-Al2O3. (C) 1997 Acta Metallurgica Inc.