Dislocation density level induced divergence between stress-free afterglow and mechanoluminescence in SrAl2O4: Eu2+, Dy3+

In this paper, we report on a new photonic behavior based on a series of photoluminescence and mechanoluminescence experiments conducted on Strontium aluminate (SrAl2O4) (SAO) co-doped with lanthanide ions such as Eu2+ (europium ion) and Dy3+ (dysprosium ion) (SAOED). It was observed that the increase of the dislocation density in SAOED decreased its stress-free afterglow while increasing its mechanoluminescence (ML). The dissimilar behavior between these two properties is yet to be reported in literature. We observed that as the lattice strain increased, the light intensity change ratio (LICR) during an applied exogenous tensile force increased while the stress-free afterglow decreased. As the crystallite size decreased, the LICR increased while the stress-free afterglow decreased. All the aforementioned observations resulted in the introduction of a newly joint stress-free afterglow-ML. mechanism where the interstitial vacancy in the SAO host lattice should be taken in consideration. Based on the trap-depth reduction model, we derived a LICR expression and predicted the current ML behavior as well for other photonic materials. The fundamental findings presented in this work will drastically change the paradigm of mechanoluminescent material design and pave the way for the full development of this technology.