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The novel compounds Ba5{V,Nb}12Sb19+x, initially found in diffusion zone experiments between Ba-filled skutterudite Ba0.3Co4Sb12 and group V transition metals (V,Nb,Ta), were synthesized via solid state reaction and were characterized by means of X-ray (single crystal and powder) diffraction, electron probe microanalysis (EPMA), and physical (transport and mechanical) properties measurements. Ba5V12Sb19.41 (a = 1.21230(1) nm, space group P4[combining overline]3m; RF(2) = 0.0189) and Ba5Nb12Sb19.14 (a = 1.24979(2) nm, space group P4[combining overline]3m; RF(2) = 0.0219) are the first representatives of the Ba5Ti12Sb19+x-type, however, in contrast to the aristotype, the structure of Ba5V12Sb19.41 shows additional atom disorder. Temperature dependent ADPs and specific heat of Ba5V12Sb19.41 confirmed the rattling behaviour of Ba1,2 and Sb7 atoms within the framework built by V and Sb atoms. Electrical resistivity of both compounds show an upturn at low temperature, and a change from p- to n-type conductivity above 300 K in Ba4.9Nb12Sb19.4. As expected from the complex crystal structure and the presence of defects and disorder, the thermal conductivity is suppressed and lattice thermal conductivity of ∼0.43 W m(-1) K(-1) is near values typical for amorphous systems. Vicker's hardness of (3.8 ± 0.1) GPa (vanadium compound) and (3.5 ± 0.2) GPa (niobium compound) are comparable to Sb-based filled skutterudites. However, the Young's moduli measured by nanoindentation for these compounds EI(Ba4.9V12Sb19.0) = (85 ± 2) GPa and EI(Ba4.9Nb12Sb19.4) = (79 ± 5) GPa are significantly smaller than those of skutterudites, which range from about 130 to 145 GPa.

The thermal stability of deformation-induced dislocations was investigated in polypropylene (PP) during annealing by means of in-situ X-ray diffraction using synchrotron radiation. The samples were cold rolled to high strains (ε = 1.2) in order to introduce a high number of dislocation lattice defects and immediately stored in liquid nitrogen afterward. Then, stepwise annealing was applied from −180 °C up to above the melting temperature (165 °C) while synchrotron X-ray diffraction patterns were recorded at each step. The resulting low noise, high angular resolution diffraction patterns were evaluated using multireflection X-ray profile analysis (MXPA), revealing parameters such as the dislocation density and the thickness of the crystalline lamellae as a function of the annealing temperature. Two significant decreases of the dislocation density were found at annealing temperatures of about 10 and 85 °C. These distinct changes in the dislocation density could be identified as the mechanisms of β- and α-relaxation, respectively, by performing additional dynamic mechanical thermal analysis (DMTA). This behavior could be attributed to an increased intrinsic mobility of the macromolecules at these temperatures accompanied by thermal activation of dislocations, resulting in their mutual annihilation or their movement into the adjacent amorphous phase. The reduction of the dislocation density at the glass transition (β-relaxation) occurs because the stabilizing effect of backstresses originating from the amorphous phase is lost. At the α-relaxation the reduction in the dislocation density is attributed to defect propagations within the crystalline lamellae as well as in the amorphous phase and the recrystallization of intralamellar mosaic blocks (i.e., grains).