Luminescence and Photochromism in Lanthanide-Doped Hackmanites

Hackmanites are a class of materials that exhibit diverse and intriguing optical characteristics, including luminescence andtenebrescence. Doping with other luminescent species would unveil a fresh spectrum of optical properties and potentialapplications. This project aimed to successfully dope a lithium derivative of hackmanite with highly luminescent lanthanides (Sm³⁺, Eu³⁺, Tb³⁺, and Dy³⁺) using a doped aluminosilicate precursor, LiAlSiO₄. Initial structural analysis indicated successfuldoping with little disruption to the host lattice. Luminescence spectroscopy revealed that the emissive properties of the lanthanideions were largely suppressed upon incorporation into the sodalite due to the presence of other highly luminescent impurities.However, europium-doped samples exhibited emission from both Eu²⁺ and Eu³⁺, with the former resulting in long-lasting greenpersistent luminescence. Room-temperature persistent luminescence was determined to arise from traps at a depth of 0.3 eV. Incontrast, doping with samarium yielded a photochromic response atypical of traditional hackmanites, characterized by absorptionextending into the near-infrared region. Spectroscopic evidence suggested the involvement of Sm²⁺/Sm³⁺ redox processes coupledto disulphide photochromic centers in the tenebrescence mechanism. Lanthanide doping provides a versatile route for modifyingboth the luminescence and photochromic behavior of hackmanites, enabling additional functionalities in lighting applicationsand UV dosimetry.