Characterization of phase structures in semiconducting SnWO4 powders by Mossbauer and Raman spectroscopies

被引:43
作者
Solis, JL [1 ]
Frantti, J
Lantto, V
Haggstrom, L
Wikner, M
机构
[1] Univ Oulu, Microelect Lab, FIN-90571 Oulu, Finland
[2] Univ Uppsala, Dept Phys, S-75121 Uppsala, Sweden
[3] Univ Nacl Ingn, Fac Ciencias, Lima, Peru
来源
PHYSICAL REVIEW B | 1998年 / 57卷 / 21期
关键词
D O I
10.1103/PhysRevB.57.13491
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Stannous tungstate, SnWO4, crystallizes in the low-temperature alpha and high-temperature beta phases. alpha-SnWO4, powders were prepared by heating an equimolar mixture of SnO and WO3 either in vacuum or in argon atmosphere at 600 degrees C for 15 h. The high-temperature beta phase was obtained as metastable at room temperature after heating the mixture at 800 degrees C and rapid quenching. In addition to x-ray-diffraction studies, Sn-119 Mossbauer and Raman spectroscopies were used as "local" probes for the characterization of the phase structures in the semiconducting and gas-sensitive powders. The composition of the powders was measured by the energy-dispersive spectroscopy of x rays. Mossbauer spectroscopy, especially, as a very local probe for tin atoms gave valuable information of small extra phase(s) in the alpha- and beta-SnWO4 powders originating in the oxidation of Sn2+ ions in the SnWO4 structures into the Sn4+ form. The Sn2+ Mossbauer doublet from both ct and beta phases showed some asymmetry not published before. The asymmetry was possible to relate to the Goldanskii-Karyagin effect with calculations based on published results for the atomic positions and thermal displacement parameters in the x-ray temperature factor of the alpha- and beta-SnWO4, structures. Raman spectra are given together with peak frequencies from a curve fit for both alpha- and beta-phase powders. The symmetries and selection rules of the normal modes at the center of the Brillouin zone are also given for both alpha and beta phases.
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页码:13491 / 13500
页数:10
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