  We report crystal growth and below 2.5K superconductivity of Nb0.25Bi2Se3.
These crystals are grown by self flux method. The X-ray diffraction (XRD)
pattern of as grown crystal flake shows (00l) plane (c-orientation) growth. The
Rietveld refinement of crushed crystal powder XRD (PXRD) pattern confirms the
phase purity of the studied sample having R-3m space group of rhombohedral
crystalline structure. The Raman spectrum of the studied Nb0.25Bi2Se3 crystal
distinctly shows three well defined vibrational modes in terms of A11g, Eg2,
A21g at around 72, 129 and 173cm-1, which are slightly shifted in comparison to
pure Bi2Se3. Magnetization studies in terms of field cooled (FC) and Zero field
cooled (ZFC) magnetic susceptibility measurements show the diamagnetic
transition (Tconset) of the compound at around 2.5K and near saturation of the
same below around 2.1K. The isothernal magnetization (MH) being taken at 2K,
revealed the lower critical field (Hc1) of around 50Oe and the upper critical
field (Hc2) of 900Oe. It is clear the studied Nb0.25Bi2Se3 is a bulk
superconductor. The superconducting critical parameters thus calculated viz.
the coherence length, upper and lower critical fields and superconducting
transition temperature for as grown Nb0.25Bi2Se3 single crystal are reported
here.
