Pressure-induced irreversible isosymmetric transition ofTSb₃(T=Co, Rh and Ir)

From Occupied Voids to Nanoprecipitates: Synthesis of Skutterudite Nanocomposites in situ

“…Since appreciable dislocation formation in CoSb 3 crystallites is not likely above 0.3 Td ( Td : peritectic decomposition T ) and the Td of CoSb 3 is 876 °C, few crystallite‐strain‐dominating dislocations are produced in the HT‐processed sample, while they are replete in the RT‐processed sample. The observed lattice‐parameter expansion and CoSb 2 formation are due to antimony self‐insertion, as previously reported49–51 and the subsequent collapse of the CoSb 3 phase under Giga‐Pascal pressures. As above, the effect is more pronounced in the RT‐processed sample as compared to the HT‐processed sample as (1) the strain energy (attendant with dislocations) is higher in the RT sample; and (2) Sb de‐insertion occurs at temperatures greater than 180 °C (at ambient pressure) as reported by Miotto et al50 Hence Sb de‐insertion, nucleation, and growth occur upon cooling the HT sample from 400 °C to room temperature.…”

Antimony desinsertion reaction from SbxCoSb3−x

“…Furthermore, in experiments conducted with CoSb 3 (and related compounds) at high pressure and room temperature, Sb x CoSb 3Àx is observed with no apparent contamination from CoSb 2 . 10, 13 As we shall see, Bragg peaks from free Sb formed by decomposition of CoSb 3 will be identified in the x-ray powder diffraction pattern of samples previously rich in Sb x CoSb 3Àx , after heating to temperatures high enough to promote the desinsertion reaction.…”

“…Also, further evidence of this transition has been provided by Matsui et al in a recent study of the pressure behavior of TSb 3 (T ¼ Co, Rh, and Ir). 13 In this work, samples of Sb x CoSb 3Àx were produced at high pressure and high temperature aiming to obtain further insight on the nature of the guest atom. Also, the change with temperature of the crystallographic site occupied by the atoms that collapses into the skutterudite cages was explored by means of model-independent charge density maps derived from synchrotron radiation x-ray powder diffraction data.…”

Structural Instability of Unfilled Skutterudite CompoundsMX3(M= Co, Rh, and Ir;X= As and Sb) under High Pressure

“…We have verified this phenomenon of CoSb 3 by synchrotron powder X-ray diffraction. 13) If the self-insertion reaction scenario is plausible, a marked rattling effect of the inserted Sb ions to site 2a, which is located inside a distorted cage, is expected.…”