Strontium lithium zinc phosphate glasses doped with holmium ions [(60-x)P2O5–20ZnO–10SrO–10LiF–xHo2O3 (0.5 ≤ x ≤ 2.0)] were synthesized via melt quenching for photonic applications. X-ray diffraction confirmed their amorphous nature, whereas scanning electron microscopy images revealed their surface morphology. Fourier-transform infrared (FTIR) and Raman spectroscopy confirmed the presence of phosphate functional groups. The oscillator strengths (Pexp and Pcal) and Judd–Ofelt parameters (Ω2, Ω4, and Ω6) were derived from the absorption spectra using the Judd–Ofelt (JO) theory. Notably, the hypersensitive transition (5I8→5F1 + 5G8) of the Ho3+ ions exhibited high oscillator strengths, with the SLZPHo0.5 glass exhibiting the highest. JO parameters ranged from 0.06 to 0.58 × 10–20 cm2 (Ω2), 0.92–4.57 × 10–20 cm2 (Ω4), and 0.64–3.31 × 10–20 cm2 (Ω6). The SLZPHo0.5 glass exhibited higher total radiative transition probabilities (AT: 15,553 s−1) and lower radiative lifetime (τR: 64 s−1) for the 5G6 level. The photoluminescence (PL) spectra at 455 nm revealed peaks at 545 nm (5F4→5I8: green), 659 nm (5F5→5I8: red), and 752 nm (5F4→5I7: red), with the 545 nm peak indicating strong green emission. The Commission Internationale de’Eclairage (CIE 1931 (x, y) coordinates and correlated color temperature (CCT) values clearly show that the present glasses are useful for yellow-green laser and display-device applications. The luminescence decay of the 545 nm luminescence (5F4→5I8 transition) showed a double exponential decay curve, and because of concentration quenching, the mean lifetimes decayed quickly from 1.8 to 1.2 ms. Among the studied glasses, the SLZP glass doped with 0.5 mol% Ho3+ exhibited strong green luminescence at 545 nm, a large stimulated emission cross-section (14.34 × 10–22 cm2), high branching ratio (57.66%), bandwidth gain (8.04 × 10–28 cm3), mean lifetime (1.8 ms), and high CCT value of 4985 K. The results indicate that SLZP glasses doped with 0.5% Ho3+ ions are the most suitable for green lasers and color display devices.

Synthesis and characterization of strontium lithium zinc phosphate glasses incorporated with holmium ions for visible green light-emitting applications

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发表日期：

2025年4月18日

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S. Vidya Sagar,
S. Babu,
K. Venkata Rao,
C. Venkateswarlu

摘要

Strontium lithium zinc phosphate glasses doped with holmium ions [(60-x)P₂O₅–20ZnO–10SrO–10LiF–xHo₂O₃ (0.5 ≤ x ≤ 2.0)] were synthesized via melt quenching for photonic applications. X-ray diffraction confirmed their amorphous nature, whereas scanning electron microscopy images revealed their surface morphology. Fourier-transform infrared (FTIR) and Raman spectroscopy confirmed the presence of phosphate functional groups. The oscillator strengths (P_exp and P_cal) and Judd–Ofelt parameters (Ω₂, Ω₄, and Ω₆) were derived from the absorption spectra using the Judd–Ofelt (JO) theory. Notably, the hypersensitive transition (⁵I₈→⁵F₁ + ⁵G₈) of the Ho³⁺ ions exhibited high oscillator strengths, with the SLZPHo_0.5 glass exhibiting the highest. JO parameters ranged from 0.06 to 0.58 × 10^–20 cm² (Ω₂), 0.92–4.57 × 10^–20 cm² (Ω₄), and 0.64–3.31 × 10^–20 cm² (Ω₆). The SLZPHo_0.5 glass exhibited higher total radiative transition probabilities (A_T: 15,553 s⁻¹) and lower radiative lifetime (τ_R: 64 s⁻¹) for the ⁵G₆ level. The photoluminescence (PL) spectra at 455 nm revealed peaks at 545 nm (⁵F₄→⁵I₈: green), 659 nm (⁵F₅→⁵I₈: red), and 752 nm (⁵F₄→⁵I₇: red), with the 545 nm peak indicating strong green emission. The Commission Internationale de’Eclairage (CIE 1931 (x, y) coordinates and correlated color temperature (CCT) values clearly show that the present glasses are useful for yellow-green laser and display-device applications. The luminescence decay of the 545 nm luminescence (⁵F₄→⁵I₈ transition) showed a double exponential decay curve, and because of concentration quenching, the mean lifetimes decayed quickly from 1.8 to 1.2 ms. Among the studied glasses, the SLZP glass doped with 0.5 mol% Ho³⁺ exhibited strong green luminescence at 545 nm, a large stimulated emission cross-section (14.34 × 10^–22 cm²), high branching ratio (57.66%), bandwidth gain (8.04 × 10^–28 cm³), mean lifetime (1.8 ms), and high CCT value of 4985 K. The results indicate that SLZP glasses doped with 0.5% Ho³⁺ ions are the most suitable for green lasers and color display devices.