Effect of quenching rate on the structure, ion transport, and crystallization kinetics in lithium-rich phosphate glass

Abstract

The report investigates the effect of quenching rate on the structure, lithium ion dynamics, and crystallization kinetics of mol% 60Li₂O–40P₂O₅ glass. Quenching rate of the order of 10⁵ K s⁻¹ has been achieved using a twin-roller rapid quenching setup. Raman and FT-IR studies reveal that the rapidly quenched glass is more disordered with a reduced amount of pyrophosphate structural units (P₂O₇ ⁴⁻) in the glass matrix as compared with the conventionally quenched glass. Non-isothermal differential scanning calorimetry brings out that the rapidly quenched glass undergoes three-phase crystallization while the conventionally quenched glass depicted predominantly single-phase crystallization. The phases are identified as lithium metaphosphate (LiPO₃), pyrophosphate (Li₄P₂O₇), and orthophosphate (Li₃PO₄). The activation energy for crystallization for the major phase Li₄P₂O₇ calculated using thermoanalytical methods turns out to be 287 kJ mol⁻¹. The above structural differences between the rapidly and conventionally quenched glasses result in superior conduction characteristics for the rapidly quenched glass depicting ionic conductivity of 1.0 × 10⁻⁶ S cm⁻¹ at 343 K with an activation energy of 0.63 eV for lithium ion motion. Microstructural studies on the glass ceramics divulge surface, 2D, and 3D crystal growth mechanism for lithium meta-, pyro-, and ortho-phosphate phases, respectively.