LASER-INDUCED SOLID-SOLUTION OF THE BINARY NANOPARTICLE SYSTEM AL2O3-ZRO2

Nanoparticles of the system Al2O3-ZrO2 were produced by simultaneous v aporization of Al2O3 and ZrO2 microparticles with the radiation of a 1 000 W Nd:YAG-laser and subsequent condensation of the induced vapor in a controlled atmosphere. The nanoparticles were investigated by trans mission electron microscopy (TEM), energy dispersive X-ray analysis (E DX), electron diffraction (ED) and X-ray diffraction (XRD). The analys is 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 crysta ls showed the existence of a so lid solution of the binary system Al2O 3-ZrO2, which is formed during the particle nucleation and rapid quenc hing. XRD measurements of the powder reveal the presence of ZrO2 in th e 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 powder s were thermally treated at a temperature T-s = 700 degrees C, the dif fraction patterns assigned to the solid solution vanished in the XRD a nd ED spectra due to decomposition of the particles as supported by ED X 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 part icles started transforming into their equilibrium phase assembly, m-Zr O2 and alpha-Al2O3. (C) 1997 Acta Metallurgica Inc.