  We studied nanoprecipitates and defects in p-type filled skutterudite
CeFe4Sb12 prepared by non-equilibrium melt-spinning plus spark plasma sintering
method using transmission electron microscopy. Nanoprecipitates with mostly
spherical shapes and different sizes (from several nm to several tens of nm)
have been observed. The most typically observed nanoprecipitates are shown to
be Sb-rich. Superlattices with a periodicity of about 3.576 nm were induced by
the ordering of excessive Sb atoms along the c direction. These
nanoprecipitates usually share coherent interfaces with the surrounding matrix
and induce anisotropic and strong strain fields in the surrounding matrix.
Nanoprecipitates with compositions close to CeSb2 are much larger in size (~ 30
nm) and have orthorhombic structures. Various defects were typically observed
on the interfaces between these nanoprecipitates and the matrix. The strain
fields induced by these nanoprecipitates are less distinct, possibly because
part of the strains has been released by the formation of defects.
