Luminescence emission from metastable Sm2+ defects in Y PO4:Ce,Sm

Area of Science:

• Materials Science
• Solid State Physics
• Luminescence

Background:

• Cerium (Ce3+) and Samarium (Sm3+) ions form stable defect centers in Yttrium Phosphate (YPO4).
• Irradiation can alter the charge states of these dopants, creating metastable Ce4+ and Sm2+ defects.
• These modified charge states serve as a model for studying carrier dynamics in charge storage phosphors.

Purpose of the Study:

• To investigate the luminescence emission behavior of metastable Sm(2+) defects in YPO4 after X-ray irradiation.
• To characterize the optical properties and transitions of Sm(2+) in this host material.
• To understand the influence of irradiation dose and temperature on Sm(2+) luminescence.

Main Methods:

• X-ray irradiation of co-doped YPO4:Ce,Sm samples.
• Photoluminescence (PL) spectroscopy to monitor emission properties.
• Variable temperature measurements to study quenching effects.

Main Results:

• Simultaneous monitoring of luminescence from both stable Sm(3+) and metastable Sm(2+) is achievable.
• Sm(2+) luminescence consists of narrow lines (1.5-1.8 eV) attributed to 4f-4f transitions, with phonon replicas (20.4 meV).
• Metastable Sm(2+) emission intensity correlates with X-ray irradiation time.
• Photoluminescence from Sm(2+) is fully quenched above 150 K due to photo-thermal ionization.

Conclusions:

• Metastable Sm(2+) defects in YPO4 exhibit distinct luminescence characteristics.
• The study provides a model system for understanding carrier dynamics and defect behavior in phosphors.
• Photo-thermal ionization significantly impacts Sm(2+) luminescence at elevated temperatures.