Tuning the Mn⁴⁺Coordination Environment in Mg₂TiO₄through a Codoping Strategy for Enhancing Luminescence Performance

Abstract

In the present work, a series of Mn+ cations (including Ca2+, Sr2+, Ba2+, Li+, Na+, or Al3+) and Mn4+ codoped Mg2TiO4 samples were synthesized through the hydrothermal–calcination route with an aim to explore the crystal structure and luminescence performance in which Mn+ acted as codoped ions. The sites of Mg2+ or Ti4+ were occupied by Mn+, resulting in a variety of coordination environments around Mn4+ ions. Through the methods of experimental characterization and theoretical simulation, the effect of codoping on the lattice structure, electronic structure, and photoluminescence properties was systematically investigated. The emission intensity of the Li/Mn codoped Mg2TiO4 sample was much higher than that of other samples, which is believed to be related to structural symmetry, codoping effect, and its relevant defect chemistry. By crystal microstructure control and ion codoping, the luminescence properties of Mn4+ must have been well regulated and optimized. The finding in this work is meaningful in the luminescence field, which may provide a strategy for developing novel photoluminescent materials.

Understanding the Efficiency of Mn4+ Phosphors: Study of the Spinel Mg2Ti1–xMnxO4

“…Rather than vibronic-induced enhancement, we interpret the increase of oscillator strength, hence the pumping capability, in Mg 2 TiO 4 :0.1% Mn 4+ , 0.5% Bi 3+ , and 0.5% Li + by the noncentrosymmetric crystal-field static perturbation in Mn 4+ produced by such nearby ions. These results are supported by a recent study in Mg 2 TiO 4 :Mn 4+ using Ca 2+ , Sr 2+ , Ba 2+ , Li + , Na + , or Al 3+ as codopant ions . These effects are important to understand why the Mn-concentration dependence of the PL intensity does not scale with the corresponding lifetime measurements following eq and is 7 times weaker than the PL intensity attained in the triply doped crystal for the same Mn 4+ concentration of 0.1 mol %.…”

“…These results are supported by a recent study in Mg 2 TiO 4 :Mn 4+ using Ca 2+ , Sr 2+ , Ba 2+ , Li + , Na + , or Al 3+ as codopant ions. 51 These effects are important to understand why the Mn-concentration dependence of the PL intensity does not scale with the corresponding lifetime measurements following eq 4 and is 7 times weaker than the PL intensity attained in the triply doped crystal for the same Mn 4+ concentration of 0.1 mol %. Besides, the expected concentration dependence of the emission intensity does not match the observed intensity.…”

Site Preference-Driven Mn4+ Stabilization in Double Perovskite Phosphor Regulating Quantum Efficiency from Zero to Champion

“…Furthermore, the increased distortion of the [WO 6 ] octahedron should also be responsible for the luminescence enhancement of Mn 4+ . ,, It is well known that the 3d–3d forbidden transition probability of Mn 4+ with 3d 3 configuration is largely determined by the local symmetry of [MnO 6 ] coordination octahedron. By co-substitution of Na + + La 3+ for 2Ca 2+ , the symmetric distortion of [WO 6 ] increased severely, which is illustrated by the bond length and angle distortions of the octahedrons as listed in Table .…”

Modified Sol-Gel Method of Synthesising a Mn4+-Doped Mg2TiO4: A Red Phosphor for Improved LED Performance

“…The doped Mn 4+ ions penetrate the host Mg2TiO4 compound structure, and a partial replacement of Ti 4+ ions generate MnO 2with a cubic shape [38,39]. Figure 6 shows FTIR of Mg2TiO4:Mn 4+ , the absorption bands at (462.92, 478.35) cm -1 are ascribed to bending vibrations and asymmetric stretching vibrations of the Mg-O bond [40], whereas the band at 570.93 cm -1 corresponds to Ti-O bond stretching vibrations [41]. Furthermore, the band at 1743.66 cm -1 could be attributed to the Mg-O-Ti bond stretching vibrations.…”