Solid-State Vitrification of LiPO3 PThrough Mechanical Milling

DRX, DSC and 31P/7Li-NMR data from crystaline and glassy LiPO3 submitted to planetary ball milling.
A novel glass state of LiPO3 was obtained in powders produced by mechanical planetary ball milling of the crystal phase, in a direct room temperature solid-state process. X-ray diffraction shows that the amorphization develops through the compression along the [2 0 2] direction. This new material shows the calorimetric signatures of the glass state (glass transition and crystallization), and is produced in an excited state relaxing the excess of enthalpy through an exothermic event below the glass transition, akin to bulk glasses produced by hyperquenching of their melts. 31P nuclear magnetic resonance (NMR) reveals the progressive amorphization of the particles: the collapse of the resonances from P crystallographic sites and the appearance of broad resonances from amorphous domains. The nature of this glass is different from those obtained through melt-quench of bulk samples. The glass transition (Tg = 303 oC) and crystallization (Tc = 350 oC) temperatures are lower than in the melt-quenched glass (Tg = 330 oC, Tc = 379 oC). Also, 31P-NMR shows a broader distribution of environments around Q2 phosphates, and higher populations of Q1 and Q3, suggesting differences in middle-range order. The amorphization can be fully reversed by recrystallization of the powders at 333 oC.