Laser ablation condensation and phase change of Ni1−xCoxO nanoparticles

Pulse laser irradiation of Ni, Co, and Co–Ni (or Ni–Co) targets in an oxygen background gas produced nanocondensates with rock salt-type structure. Analytical electron microscopic observations indicated that such nanocrystals are cubic in shape for NiO and cubo-octahedral for Co1−xO and Ni1−xCoxO. The nanocrystals coalesced predominantly with {1 0 0} or {1 1 1} facets to form nano chain aggregates or closer packed manner. The Co1−xO was more or less oxidized as Co3−δO4 spinel with modulated distribution of defect clusters as indicated by diffuse side-band diffractions.