Observation of anion states of tin in Sr3-xSnO

In an antiperovskite oxide Sr3SnO, an anionic state is naively expected for tin such as (Sr2+)3Sn4-O2-. Since tin is a metallic element and tends to be cations like Sn2+ and Sn4+, the “charge-inverted” state Sn4− is unusual and very rare in oxides. However, it has not been experimentally investigated how many electrons tin actually possesses in antiperovskite oxides.

We made use of the Mössbauer effect to investigate the ionic state of tin. In Mössbauer spectroscopy, the state of tin can be deduced by examining γ ray with what wavelength a material absorbs. (γ ray is the light with a wavelength much shorter than that of ultraviolet.) As a result, we confirmed that Sn4− is realized in Sr3SnO (Figure). Furthermore, we revealed that inside Sr3−xSnO with less strontium, tin atoms neighboring the vacancy of strontium (indicated by ‘x‘ of 3−x) are in yet another state than Sn4−. This is the first observation of anionic states of tin in oxides. Through this discovery, we expect that antiperovskite oxides, with unusual metallic anions, will obtain more attention.

This research is a collaboration with Prof. Seto’s laboratory at the Institute for Integrated Radiation and Nuclear Science, Kyoto University. The article information is listed below, but those who are not researchers or have not subscribed to Physical Review B can also view the article from Kyoto University Repository for Navigating Academic Information (KURENAI).

Mössbauer spectra of Sr3SnO (left) and Sr3−xSnO (right). The horizontal axis is the energy of γ ray and the vertical axis is transmission. Since the sample absorbs the γ ray with the same energy as that absorbed by Mg2Sn, it is concluded that Sr3SnO contains Sn4−. Moreover, absorption of a γ ray with a different enerby by Sr3−xSnO points out another ionic state of tin.

Article information

Ikeda, A; Koibuchi, S; Kitao, S; Oudah, M; Yonezawa, S; Seto, M; Maeno, Y

Negative ionic states of tin in the oxide superconductor Sr3-xSnO revealed by Mössbauer spectroscopy Journal Article

In: Physical Review B, vol. 10, no. 24, pp. 245145, 2019.

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