Gas-phase preparation of L1 0 ordered FePt nanoparticles

Abstract

We present a technique to prepare FePt nanoparticles from the gas-phase which aims to obtain L1 0 ordered FePt nanoparticles by thermal sintering in the gas-phase. The particles in the size range 3– 20 nm are generated via inert-gas condensation using DC-sputtering at very high pressures in the mbar range. Prior to their deposition, the particles are thermally sintered in the gas-phase at temperatures between 293 and 1273 K. The particles are mainly investigated by (high resolution) transmission electron microscopy. Depending on the inert-gas pressure and the sintering temperature, the morphology and the structure of the FePt nanoparticles changes dramatically. FePt nanoparticles prepared at 0.5 mbar show no agglomeration and, therefore, have a very small size distribution with a geometrical standard deviation of σ g=1.1. Using pressures p⩾1.0 mbar , we observe particle agglomeration and broadening of the particles size distribution. While particles prepared at p=0.5 mbar show icosahedral structures up to sintering temperatures of 1273 K , the preparation at p>0.5 mbar and high sintering temperatures (1273 K) leads to single crystalline particles with L1 0-ordering.