Rare‐earth‐free strong red luminescence in dense, undoped Mg ₂ TiO ₄ polycrystalline ceramics with inverse spinel structure

Abstract

Abstract Rare‐earth element (REE)‐based luminescent materials are widely used in laser and lighting applications, but their sustainability is limited by intensive mining, complex processing, and limited recyclability. Addressing this challenge, we report (for the first time) strong red photoluminescence from highly dense (∼97 ± 1%), phase‐pure inverse spinel Mg 2 TiO 4 ceramics processed via conventional pressureless sintering. Intense red emissions, mainly originating from self‐trapped excitons, were noted in the range of 658–673 nm, indicating strong electron‐phonon coupling. The excitation spectra revealed a peak at 485 nm with an optical band gap of 2.56 eV. A variety of sample geometries and sizes consistently exhibited robust and stable red luminescence, without the need for external dopants or rare‐earth elements. Photoluminescence and fluorescence lifetime measurements conducted over 25–325 K determined an average lifetime of 0.39 µs at room temperature. Electron paramagnetic resonance spectroscopy analysis further confirmed oxygen vacancy‐related defect states, with indications of additional defect centers. Overall, these findings portray Mg 2 TiO 4 ceramic as a sustainable and high‐performance alternative to REE‐based phosphors for red‐emitting laser applications.

Affiliated Institutions

• Indian Institute of Technology Patna IN

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