Formation and structure of Na2S + P2S5 amorphous materials prepared by melt-quenching and mechanical milling

xNa(2)S + (1 - x)P2S5 amorphous and partially crystalline materials were prepared by melt-quenching and mechanical milling. These products were characterized using x-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Compared to the narrower x-ray amorphous range for this system obtained through melt-quenching as found in this study, 0.50 <= x <= 0.67, the x-ray amorphous range for this system could be extended from the low-alkali ultra-thiophosphate composition of x similar to 0.25 to slightly above the high-alkali pyro-thiophosphate composition of x similar to 0.70 using mechanical milling. Mechanically milled samples with Na2S of composition x = 0.75 yielded a partially crystalline material that had diffuse XRD peaks associated to the alpha-Na3PS4 phase. A similar result was obtained for the x = 0.80 composition except that, as expected, it also showed peaks for unreacted (over stoichiometric) Na2S. The melt-quenched and mechanically milled samples with the same compositions 0.50 <= x <= 0.67 showed similar FT-IR and Raman spectra, indicating very similar chemical short-range structures are present in both of these amorphous materials. It was found that the Na2S + P2S5 system exhibited similar behavior to that of the Li2S + P2S5 in that chemical reaction between Na2S and P2S5 could be induced by mechanical milling near room temperature to produce both amorphous and polycrystalline materials. (C) 2011 Elsevier B.V. All rights reserved.