Adjusting luminescence properties of ZnAl 2 O 4 :Mn 2+ (Mn 4+ ), Li + phosphors through cation substitution.

ZnAl ₂ O ₄ 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, Mn ⁴⁺ ions have emerged as one of the most promising activators. Considering the price advantage of MnCO ₃ generating Mn ²⁺ ions and the charge compensation effect potentially obtaining Mn ⁴⁺ ions from Mn ²⁺ ions, this research delves into a collection of ZnAl ₂ O ₄ :Mn ²⁺ (Mn ⁴⁺ ), x Li ⁺ (x = 0%-40%) phosphors with Li ⁺ as co-dopant and MnCO ₃ as Mn ²⁺ 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 Zn ²⁺ lattice sites. Furthermore, Li ⁺ ion doping was assuredly found to facilitate the oxidization of Mn ²⁺ to Mn ⁴⁺ , 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.
(© 2024 John Wiley & Sons Ltd.)