Raman and x-ray diffraction studies of nanometric Sn₂P₂S₆crystals

Abstract

Nanometric Sn2P2S6 crystalline powders and ceramics are studied by x-ray diffraction and Raman spectroscopy. The average crystallite size is estimated from TEM and x-ray data. The observed features in the Raman spectra are discussed in view of confinement-related selection rules relaxation, surface phonon modes and possible partial substitution of sulfur by oxygen at the nanometric powder surface.

Annealing-induced formation of Sn2P2S6 crystallites in As2S3-based glass matrix

“…Besides, the maxima at 142, 183, and 244 cm . Note that the frequency positions of all these bands correlate with the known Sn 2 P 2 S 6 phonon spectrum [9] as well as with our earlier measurements for Sn 2 P 2 S 6 micro-and nanopowders and ceramics where features near 85, 140, 185, 245, 260, and 290 cm −1 were observed [22]. The observed features clearly confirm Sn 2 P 2 S 6 crystallite formation in the glass matrix under annealing.…”

“…The slight difference in frequency can evidently be explained by the different long-range environment somewhat distorting the rings under consideration. It should also be mentioned that in our earlier study of Sn 2 P 2 S 6 nanocrystals obtained by ball milling we observed the weak band centred at 406 cm −1 , assumed to stem from partial S→O substitution in PS 3 pyramids due to oxidation at the nanocrystal surface [22]. The band of similar frequency at 411 cm −1 was observed in the Raman spectra of Sn 2 P 2 S 6 crystals recovered after highpressure treatment, where it was possibly related to pressure-induced defects [39].…”

“…In Sn 2 P 2 S 6 ceramics with grain sizes below 1 μm a decrease of the phase transition temperature by 12 K with respect to the bulk sample was observed in dielectric measurements [19]. Nanocrystalline Sn 2 P 2 S 6 powders with average crystallite sizes down to 20 nm were obtained earlier using soft chemistry (exchange reaction in an aqueous medium) [20,21], ball milling from single crystals [22], and ball milling from elemental components with subsequent microwave treatment [23]. Fabrication and investigation of nanoscale ferroelectric materials are important in view of both fundamental and practical aspects.…”

Ferroelectric nanoparticles in low refractive index liquid crystals for strong electro-optic response

“…The nanoparticles were prepared by milling microparticles of SPS, and then separately BaTiO 3 , ͑Х1 m size͒, with oleic acid for 100 h. The expected size of nanoparticles was of the order of 10 nm, based on the published transmission electron microscopy ͑TEM͒ images of SPS powder after 25-75 h of milling. 11 However, while those TEM images allowed some important size characterization of nanoparticles, their shape and distribution was difficult to resolve in detail. Recently, high-resolution images of BaTiO 3 nanocrystals, using AFM in tapping mode, were published 12 and, therefore, in our analysis, we opted for this technique.…”

Raman scattering in chalcogenide‐based ferroelectrics: from bulk to nanoscale

“…For each of the compounds microcrystalline powders of various grain size were obtained by ball milling the material in a stainless steel cylindrical vial, depending on the milling process duration. Transmission electron microscopy and X-ray diffraction showed that the finest powder fractions obtained after 75-h and 50-h milling contained near-spherical Sn 2 P 2 S 6 nanocrystals with average size down to 9 nm [7] and rod-shaped SbSI crystallites with transverse size down to 70 nm and length 0.5-1 µm [8]. Hence, SbSI appeared to be much harder in the course of attrition and to preserve the rod-like shape typical for the bulk single crystals of this compound what is quite consistent with the chain-like structure of SbSI.…”