Optical and magnetic properties of Ni/NiO nanopartilces in YSZ by metal ion implantation and post-implantation annealing

Sixty four keV Ni+-ion implantation in yttria-stabilized zirconia (YSZ) was conducted at the room temperature up to a fluence of 1×1017 ion/cm2. The as-implanted crystals were annealed isochronally at temperatures up to 900 °C in ambient atmosphere. Optical absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and a superconducting quantum interference device (SQUID) magnetometer have been utilized to characterize the samples. XPS results showed that the charge state of Ni was mainly Ni0 in as-implanted and Ni2+ in annealed samples. However, TEM analysis did not reveal any obvious metallic Ni nanoparticles or amorphization of YSZ after ion implantation. After annealing, NiO nanoparticles with size ranging from 4 to 12 nm were observed. The larger nanoparticles distributed near the surface of the YSZ. High-resolution TEM image clearly demonstrated the crystallinity of the nanoparticles. Optical absorption spectroscopy did not clearly detect the absorption bands of Ni or NiO nanoparticles. Magnetic measurement indicated that the coercive force of residual Ni nanoparticles was ∼270 Oe at 10 K in annealed crystals.