Synthesis of skutterudite superlattices by controlled crystallization of elementary modulated reactants

Abstract

Modulated elemental reactants were used to prepare a number of superlattices containing ternary skutterudites. For the superlattice [LaCo/sub 4/Sb/sub 12/]/sub n/[YCo/sub 4/Sb/sub 12/]/sub m/, low angle diffraction maxima from the superlattice structure were observed. Diffraction data collected as a function of annealing time and temperature are presented which show the evolution of the initially amorphous modulated reactant into the desired superlattice. For the [LaCo/sub 4/Sb/sub 12/]/sub n/[LaFe/sub 4/Sb/sub 12/]/sub m/ superlattice, rocking curve data were collected on both the low and high angle diffraction maxima. These data demonstrate that the skutterudite grains are randomly oriented with respect to the original superlattice but the chemical modulation of the superlattice is aligned with the substrate. Attempts to prepare skutterudite superlattices containing unfilled skutterudites were unsuccessful at short modulation distances, implying the facile inter diffusion of both the ternary cation and the transition metal through the empty cage sites in the structure.