Effects of CaF2 addition on the structure, optical properties, and chemical durability of phosphate glasses

Abstract

A series of aluminum phosphate glasses doped with 0.01 copper oxide (CuO) has been prepared by the melting-quench method. Calcium fluoride (CaF₂) was introduced as a network modifier, partially substituting phosphate (P₂O₅), to examine its effects on structural, thermal, chemical, and optical properties. Thermal Mechanical Analysis (TMA) results indicate that CaF₂ incorporation reduces the glass transition temperature (T_g) from 623 °C to 599 °C. X-ray diffraction (XRD) identify samples were amorphous. Structural analyses using Nuclear Magnetic Resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) confirmed the formation of (PO₃)-F terminal bonds, resulting in improved chemical durability through the reduction of P–OH bond formation. Furthermore, UV–visible spectroscopy revealed that the addition of CaF₂ increases the optical band gap associated with copper ions from 3.71 eV to 3.95 eV. This study demonstrates that incorporating up to 0.0792 CaF₂ enhances the chemical durability of phosphate glasses by approximately 20 %, suggesting potential benefits for developing stronger and more efficient optical materials.