A Thermodynamic-Guided Spark Plasma Sintering Approach for the Fabrication of High-Performance Fluorophosphate Glasses

Fluorophosphate (FP) glasses are promising materials for advanced photonic applications, yet their performance is often compromised by challenges in conventional high-temperature melting (HTM) synthesis, such as fluoride volatilization and hydroxyl contamination. This study introduces a comprehensive strategy to overcome these limitations by integrating thermodynamic prediction with an advanced fabrication technique. First, a thermodynamic method was employed to successfully predict the glass-forming region (GFR) of the RF n –AlF 3 –Sr(PO 3 ) 2 system, enabling the rational design of FP compositions with excellent anti-crystallization stability (Δ T > 100°C), a high elastic modulus (up to 123.2 GPa), and a low nonlinear refractive index (1.06–1.17 × 10 −13 esu). Subsequently, a comparative investigation was conducted on Nd 3+ -doped MgF 2 –AlF 3 –Sr(PO 3 ) 2 –Ba(PO 3 ) 2 glasses prepared by conventional HTM and spark plasma sintering (SPS). The results demonstrate that the rapid, low-temperature, vacuum‑assisted SPS process significantly enhances fluorine retention by up to 76% and drastically reduces the hydroxyl absorption coefficient from over 10 to 0.09 cm −1 , which induce structural modifications and favorably alters the physical and 4 F 3/2 → 4 I 9/2 transition properties of Nd 3+ -doped FP glasses. Specifically, glasses fabricated via SPS exhibit higher hardness, reduced nonlinear effects, enhanced emission intensity, a more symmetric local ligand field, and an increase in fluorescence lifetime by up to 38%. This work establishes an efficient paradigm for developing high-performance FP glasses and provides fundamental insights into their composition–processing–structure–property relationship, paving the way for next-generation optical materials and devices.