  Superconductivity has been explored in single crystals of the Ni-doped
FeAs-compound SrFe2-xNixAs2 grown by self-flux solution method. The
antiferromagnetic order associated with the magnetostructural transition of the
parent compound SrFe2As2 is gradually suppressed with increasing Ni
concentration x and bulk-phase superconductivity with full diamagnetic
screening is induced near the optimal doping of x = 0.15 with a maximum
transition temperature Tc ~9.8 K. An investigation of high-temperature
annealing on as-grown samples indicate that the heat treatment can enhance Tc
as much as ~50 %.
