Quenching cooperative transitions by destroying Yb³⁺-clusters

Area of Science:

• Materials Science
• Luminescence Spectroscopy
• Solid-State Physics

Background:

• Previous work demonstrated cooperative luminescence of Yb³⁺ trimers and Yb³⁺ tetramer-sensitized Gd³⁺ luminescence in CaF₂.
• Rare-earth ion-doped materials exhibit complex luminescence behaviors influenced by ion clustering and energy transfer.

Purpose of the Study:

• To experimentally investigate the unusual luminescence phenomenon of Gd³⁺ in CaF₂ doped with Yb³⁺ and Gd³⁺.
• To elucidate the underlying mechanism responsible for the non-monotonic upconversion luminescence of Gd³⁺.

Main Methods:

• Upconversion luminescence spectroscopy upon 980 nm laser excitation.
• Downconversion luminescence spectroscopy via direct Gd³⁺ excitation.
• Fluorescence dynamic analysis.
• Optically inactive rare-earth ion-doping experiments.

Main Results:

• Observed a non-monotonic increase and subsequent decrease in Gd³⁺ upconversion luminescence with increasing Gd³⁺ concentration (0-0.9 mol%).
• This behavior contrasts with the monotonic increase seen in direct Gd³⁺ excitation spectra.
• Identified energy transfer from Yb³⁺-tetramers to Gd³⁺ and Yb³⁺-cluster destruction as key factors.

Conclusions:

• Proposed a novel luminescence quenching mechanism: Yb³⁺-cluster destructive quenching.
• The proposed mechanism was validated through dynamic analysis and doping experiments.
• This finding offers new insights into luminescence control in rare-earth doped materials.