Structure and physical properties of Ba(PO ₃ ) ₂ –AlF ₃ –BaSO ₄ fluoro‐sulfo‐phosphate glasses

Abstract Alkali‐earth‐metaphosphate‐based fluoro‐sulfo‐phosphate M(PO ₃ ) ₂ –AlF ₃ –MSO ₄ (MPFS, M = Ca, Sr, Ba) glasses have been developed via simultaneously incorporating fluoride and sulfate into metaphosphate glass. Their glass‐forming regions were efficiently determined under the guidance of thermodynamic calculation method. The physical and structural properties of BaPFS glass were investigated in detail. Furthermore, near‐infrared spectroscopic properties of Er ³⁺ ‐doped BaPFS (Er–BaPFS) glass were studied. Physical parameters, such as Abbe's number ν _d (55‐75) and nonlinear refractive index n ₂ (1.17‐1.86 × 10 ⁻¹³ esu), of BaPFS glass are strongly depended on P/F/S ratio. The structure of BaPFS glass gradually depolymerizes and tends to become multianionic when Ba(PO ₃ ) ₂ is substituted by AlF ₃ and BaSO ₄ . Anion‐substitution strategy effectively modulates the property and structure of glass, providing a scheme to derive glass materials. In addition, enhanced emission at ~1.5 μm has been observed from Er–BaPFS glass along with large emission cross section (5.0‐5.5 × 10 ⁻²¹ cm ² ) and long lifetime (6.7‐7.3 ms), resulting in large figure of merit (3.46‐3.84 × 10 ⁻²³ cm ² ·s), which is a promising candidate for solid‐state laser.