Raman Spectroscopic Study of the Optical Phonons of Mg2Si1−xSnx Solid Solutions

Abstract

Mg2Si1−xSnx solid solutions are prepared in the composition range from x = 0 to 1 by mechanical alloying using high-energy ball milling followed by direct-current sintering at 600–800 °C. X-ray diffraction analysis confirms that the samples obtained are uniform solid solutions. Raman spectroscopy shows two first-order phonon Raman bands and a distribution of Raman signals due to second-order phonon Raman scattering. The first-order Raman bands are assigned to the nondegenerate Raman-forbidden F1u (LO) mode and the triply degenerate Raman-allowed F2g mode. Both modes exhibit a linear shift of the phonon frequency with a composition showing a clear one-mode behavior for this solid solution. The findings are discussed in the context of existing theories for the occurrence of the one-mode or two-mode behavior of phonons in solid solutions.