Research of the structure and dynamic interactions of particles in the Li0.42K0.58NO3– R (R= α-Al2O3, γ-Al2O3, SiO2) and (LiNO3–LiClO4) – γ-Al2O3 composites in various temperature conditions and phase states

Abstract The paper presents a comprehensive study of the Li0.42K0.58NO3– R (R = α-Al2O3, γ-Al2O3, SiO2) and (LiNO3 – LiClO4) - γ- Al2O3 composite salt systems by vibrational spectroscopy, X-ray diffractometry, and differential scanning calorimetry. According to the results of Raman spectra and XRD analysis, it has been found that in the case of a sufficiently small filler (15 nm-γ-Al2O3 and SiO2), an amorphous phase appears, both for systems based on Li0.42K0.58NO3 and for the nanocomposite based on (LiNO3)0.5-(LiClO4)0.5. In the case of nanocomposites based on the Li0.42K0.58NO3 system, this additionally leads to the formation of the metastable KNO3 (R3m) phase. The temperature changes in the half-widths of the corresponding bands of the Raman spectrum during the transition from a solid-phase to a molten state become less significant as the concentration of the oxide filler increases. At x≥0.7, on the temperature dependences of the half-width of the ν1 (A) band in the vicinity of the melting point, only a small kink characteristic of amorphous systems is noticed. This is confirmed by the results of thermal analysis. It has been found that the solid filler has a different effect on the processes of orientational and vibrational relaxation in the molten phases of the studied NIS, namely, the orientational mobility of NO3– decreases, while the relaxation rate of its vibrational excitation increases.