How do phosphor ceramics emit light after being excited?

Phosphor ceramics emit light through a process of luminescence, which occurs when electrons within the material are stimulated from stable, low-energy positions to higher energy levels by an external source, such as ultraviolet light, X-rays, or an electron beam.12

The specific mechanism involves the following steps:

• Excitation: Energy is transferred to the electrons, causing them to jump to higher energy levels. In many ceramic phosphors, this involves raising electrons from the valence band to the conduction band or to specific energy levels introduced by activators (dopants).34
• Energy Dissipation: As electrons transition, some energy is often lost as heat to the host-crystal lattice.4
• Emission: When the energized electrons drop back to lower, stable energy levels, the energy difference is released as light at characteristic wavelengths.14

In some cases, electrons are captured by traps—imperfections in the crystal lattice—which can delay this return and prolong the emission of light, a process known as phosphorescence.53