  Single crystalline CaFe2As2 and (Ca1-xNax)Fe2As2 polycrystals (0 < x < 0.66)
are synthesized and characterized using structural, magnetic, electronic
transport, and heat capacity measurements. These measurements show that the
structural/magnetic phase transition in CaFe2As2 at 165 K is monotonically
suppressed by the Na doping and that superconductivity can be realized over a
wide doping region. For 0.3 < x < 0.36, the magnetic susceptibilities indicate
the possible coexistence of the spin density wave (SDW) and superconductivity.
Superconducting phases corresponding to the Na doping level in (Ca1-xNax)Fe2As2
for nominal x = 0.36, 0.4, 0.5, 0.6, and 0.66, with Tc = 17 K, 19 K, 22 K, 33
K, and 33 K, respectively, are identified. The effects of the magnetic field on
the superconductivity transitions for x = 0.66 samples with high upper critical
fields Hc2 \approx 103 T are studied, and a phase diagram of the SDW and
superconductivity as a function of the doping level is thus presented.
