SrAl2O4EuDy

SrAl2O4:Eu2+,Dy3+ (often written SrAl2O4EuDy or SrAl2O4:Eu,Dy) is a persistent luminescent phosphor based on the host lattice SrAl2O4 doped with europium and dysprosium ions. The material emits green light, with a peak around 520–535 nm, and can display afterglow lasting from minutes to several hours after the excitation source is removed.

The host lattice SrAl2O4 is typically in a monoclinic crystal structure (β-SrAl2O4) and provides a framework in which Eu2+ and Dy3+ dopants substitute for Sr2+ sites. Eu2+ acts as the luminescent activator, producing broad-band emission through 4f-5d transitions, while Dy3+ serves as a trap-associated dopant that stores charge carriers and slowly releases them, enabling long-lasting afterglow.

Luminescence mechanism involves optical charging of Eu2+ ions and formation of electron traps associated with Dy3+. Upon removal of the excitation source, trapped carriers are thermally released and recombine at Eu2+ centers, yielding a continuous green afterglow. The duration and intensity of the afterglow depend on dopant concentrations, synthesis quality, and temperature history; typical formulations use Eu2+ in the range of roughly 0.5–2 mol% and Dy3+ at a few mol%.

Synthesis commonly employs high-temperature solid-state reactions (often around 1100–1500°C) in reducing or inert atmospheres to ensure Eu2+ occupancy. Alternative methods, such as sol-gel or combustion synthesis, can also produce fine powders with improved homogeneity.

Applications include glow-in-the-dark pigments for coatings, paints, safety signage, textiles, and novelty items. The material is valued for its bright green emission and long afterglow, though performance can be sensitive to environmental conditions and material processing.