Triboluminescence of Rare-Earth-Doped Celsian Polycrystals

Abstract

Triboluminescence has been observed in BaAl₂Si₂O₈ and SrAl₂Si₂O₈ doped with Eu²⁺ and Dy³⁺. From comparison between photoluminescence and triboluminescnece spectra, it is found that the emission intensity due to the 4f-4f transition of Dy³⁺ is larger in triboluminescence than in photoluminescence. It is thought that the crystal field is distorted around the rare earth ions which bring about the triboluminescence; the distorted crystal fields increase the transition propability of partly-forbidden 4f-4f transitions of Dy³⁺. On the other hand, the broad band due to the 4f-5d transition of Eu²⁺ shifts to longer wavelengths in the triboluminescence than in the photoluminescence. An increase in splitting of 5d levels and Stokes shift are possible origins for this phenomenon.