Milling-induced chemical decomposition of the surface of EuBaCo2O5.5 powders studied by means of soft X-ray absorption spectroscopy.

We present results of soft X-ray absorption spectroscopy studies of EuBaCo 2 O 5.5 powders subjected to mechanical impact (milling in a ball mill). We show that in the near-surface region (5–10 nm) of particles of the powder, EuBaCo 2 O 5.5 decomposes into Co 3 O 4 , BaCO 3 , and EuCoO 3. A knowledge of the low-spin state of Co3+ ions in EuCoO 3 and Co 3 O 4 and possibilities of surface-sensitive soft X-ray absorption spectroscopy have allowed to determine the composition of the EuBaCo 2 O 5.5 sample subjected to mechanical impact near its surface, which is inaccessible to standard X-ray phase analysis. Unlabelled Image • EuBaCo 2 O 5.5 powders are subjected to mechanical impact in a ball mill. • The samples are studied by surface-sensitive soft X-ray absorption spectroscopy. • Products of reaction in the near-surface area are Co 3 O 4 , BaCO 3 , and EuCoO 3. • Co3+ ions in EuCoO 3 are in a low-spin state. [ABSTRACT FROM AUTHOR]