Adjusting luminescence properties of ZnAl₂O₄:Mn²⁺(Mn⁴⁺), Li⁺ phosphors through cation substitution

ZnAl₂O₄ with a typical spinel structure is highly expected to be a novel rare-earth-free ion-activated oxide phosphor with red emission, which holds high actual meaning for advancing phosphor-converted light-emitting diode (pc-LED) lighting. Among the rare-earth-free activators, Mn⁴⁺ ions have emerged as one of the most promising activators. Considering the price advantage of MnCO₃ generating Mn²⁺ ions and the charge compensation effect potentially obtaining Mn⁴⁺ ions from Mn²⁺ ions, this research delves into a collection of ZnAl₂O₄:Mn²⁺(Mn⁴⁺), x Li⁺ (x = 0%-40%) phosphors with Li⁺ as co-dopant and MnCO₃ as Mn²⁺ dopant source prepared by a high temperature solid-state reaction method. The lattice structure was investigated using X-ray diffraction (XRD), photoluminescence (PL), and photoluminescence excitation (PLE) spectroscopy. Results suggest a relatively high probability of Li⁺ ions occupying Zn²⁺ lattice sites. Furthermore, Li⁺ ion doping was assuredly found to facilitate the oxidization of Mn²⁺ to Mn⁴⁺, leading to a shift of luminescence peak from 516 to 656 nm. An intriguing phenomenon that the emission color changed with the Li⁺ doping content was also observed. Meanwhile, the luminescence intensity and quantum yield (QY) at different temperatures, as well as the relevant thermal quenching mechanism, were determined and elucidated detailedly.