Highlighting of structural units of B₂O₃–Li₂O–P₂O₅ system under heat treatment

As technology evolves towards the design of small size – high efficiency devices there is a necessity for the development of solid, stable electrolytes that can be fabricated in various shapes. Accordingly, a glass system of xB₂O₃·0.4Li₂O·(0.6 − x)P₂O₅ with 0 ≤ x ≤ 0.6 mol%, was prepared by melting the raw materials at 1200 °C and rapidly cooling the melts at room temperature. The samples were afterwards heat treated to develop crystalline structures, for better identification of the units that build up the network. In order to get a deep understanding of the role played by the two glass formers on the structural characteristics, the samples were investigated by means of Raman and Fourier-Transform Infrared (FT-IR) spectroscopy. The induced modifications were also analysed in terms of structure stability given by the appearance of NBO containing units. In this way lithium containing phosphate units have been proven to be more susceptible to structural transformations. The information gathered from the vibrational analysis of the samples was completed with data derived from the X-ray diffraction (XRD) analysis. The common crystalline phase has been identified as Li₃PO₄, which is consistent with the presence of vibrational bands related the ionic Q⁰ units. - Highlights: • We investigated the two glass formers role on the structural characteristics. • P₂O₅ addition stabilizes the matrix. • Thermal treatment has a strengthening effect on the network of the samples. • Thermal treatment also decreases the number of non-bridging oxygen present in the matrix