Mössbauer 119 Sn and XPS spectroscopy of Sn 2 P 2 S 6 and SnP 2 S 6 crystals

• Published in: physica status solidi (b) Vol. 246; no. 5; pp. 1110 - 1117
• Main Authors: Vysochanskii, Yu. M., Baltrunas, D., Grabar, A. A., Mazeika, K., Fedyo, K., Sudavicius, A.
• Format: Journal Article
• Language: English
• Published: 01-05-2009
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200844316

The monoclinic Sn
2
P
2
S
6
and rombohedral layered SnP
2
S
6
crystals have been investigated by
119
Sn Mössbauer and X‐ray photoelectron spectroscopies. By comparing the isomer shift, quadrupole splitting and binding energies for Sn 3d and 4d core levels in these crystals with such parameters for the metal tin and for different tin compounds it was found that in the Sn
2
P
2
S
6
crystals Sn existed in the Sn
2+
oxidation state and in the SnP
2
S
6
crystals – in the Sn
4+
state. Temperature dependences of the isomer shift and Debye–Waller factor satisfied the Debye model in the temperature interval of 6 – 300 K for the SnP
2
S
6
crystals but deviated from such behavior at
T
> 250 K for Sn
2
P
2
S
6
crystals. This peculiarity together with specific character of the temperature dependence of the quadrupole splitting were related to the role of the stereoactive Sn 5s
2
lone pair electrons in the determined by three‐well potential mechanism of the second order ferroelectric phase transition at 337 K in Sn
2
P
2
S
6
crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)