  Monophasic and homogeneous Ni10Zr7 nanocrystalline alloy films were
successfully grown at room temperature by co-sputtering in an indigenously
developed three-gun DC/RF magnetron sputtering unit. The films could be
produced with long-range crystallographic and chemical order in the alloy, thus
overcoming the widely acknowledged inherent proclivity of the glass forming
Ni-Zr couple towards amorphization. Crystallinity of these alloys is a
desirable feature with regard to improved efficacy in applications such as
hydrogen storage, catalytic activity and nuclear reactor engineering, to name a
few. Thermal stability of this crystalline phase, being vital for transition to
viable applications, was investigated through systematic annealing of the alloy
films at 473 K, 673 K and 923 K for various durations. While the films were
stable at 473 K, the effect of annealing at 673 K was to create segregation
into nanocrystalline Ni (superparamagnetic) and amorphous Ni+Zr (non-magnetic)
phases. Detailed analyses of the physical and magnetic structures before and
after annealing were performed through several techniques effectual in
analyzing stratified configurations and the findings were all consistent with
each other. Polarized neutron and X-ray reflectometry, grazing incidence x-ray
diffraction, time-of-flight secondary ion mass spectroscopy and X-ray
photoelectron spectroscopy were used to gauge phase separation at nanometer
length scales. SQUID based magnetometry was used to investigate macroscopic
magnetic properties. Simulated annealing performed on this system using
molecular dynamic calculations corroborated well with the experimental results.
This study provides a thorough understanding of the creation and thermal
evolution of a crystalline Ni-Zr alloy.
