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

Abstract

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 solid 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 − x2) (0 < x < 1), as also confirmed by ED measurements. When the powders were thermally treated at a temperature Ts = 700°C, the diffraction patterns assigned to the solid solution vanished in t he XRD and ED spectra due to decomposition of the particles as supported by EDX and high resolution TEM measurements on single nanoparticles. At Ts ≥ 1200 °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 α-Al2O3.