Adding memory to pressure-sensitive phosphors.

Area of Science:

• Materials Science
• Solid-State Physics
• Luminescence

Background:

• Mechanoluminescence (ML) is light emission from solids under mechanical stress, used for sensing and stress visualization.
• Current ML requires real-time recording during pressure events, limiting its application.
• Energy in ML phosphors is stored by trapped charge carriers within the crystal lattice.

Purpose of the Study:

• To introduce a memory function into pressure-sensitive phosphors for delayed optical readout.
• To enable recording of the location and intensity of past pressure events.
• To investigate the underlying mechanisms in a specific phosphor material.

Main Methods:

• Utilized the BaSi₂O₂N₂:Eu²⁺ phosphor, known for its broad trap depth distribution.
• Integrated Mechanoluminescence (ML), Optically Stimulated Luminescence (OSL), and Thermoluminescence (TL) measurements.
• Analyzed the impact of light, heat, and pressure on the trap depth distribution and charge carrier dynamics.

Main Results:

• Demonstrated a memory effect in the phosphor, allowing optical readout of pressure events up to 72 hours later.
• Showed that mechanical action can redistribute trapped charge carriers, not just cause direct light emission.
• Characterized the broad trap depth distribution as crucial for enabling this memory function.

Conclusions:

• The developed phosphor possesses a memory function for recording past mechanical events.
• This innovation is expected to drive new applications in pressure sensing and damage detection.
• The findings provide a novel approach to studying charge carrier transitions in energy storage materials.