Lattice parameter evolution in Pt nanoparticles during photo-thermally induced sintering and grain growth

An in-situ optical pump/x-ray probe technique has been used to study the size dependent lattice parameter of Pt nanoparticles subjected to picosecond duration optical laser pulses. The as-prepared Pt nanoparticles exhibited a contracted lattice parameter consistent with the response of an isolated elastic sphere to a compressive surface stress. During photo-thermally induced sintering and grain growth, however, the Pt lattice parameter did not evolve with the inverse particle size dependence predicted by simple surface stress models. The observed behavior could be attributed to the combined effects of a compressive surface/interface stress and a tensile stress arising from intergranular material. [Display omitted] •This paper presents for the first time the results of a study of the lattice parameter evolution in nanometer-sized Pt particles during photo-thermally induced sintering and grain growth.•In particular, the use of an optical pump/x-ray probe technique utilizing intense picosecond (ps) duration optical laser pulses combined with the short x-ray pulses available at Argonne National Laboratory’s Advanced Photon Source has allowed the lattice parameter/particle size relationship to be studied under highly non-equilibrium thermal processing conditions.•The results of this study have shown that under intense laser excitation the Pt lattice parameter does not evolve with the simple inverse particle size dependence predicted by the Laplace equation.•The observed behavior has been analyzed in terms of a simple model in which the microstructural effects of surface and interface stresses in combination with the stress fields from intergranular material were considered.•The application of this model has allowed a number of different and apparently disparate experimental results on other small metallic particles to be rationalized.