Charge compensators achieve controlled self-reduction of Europium in BaMgP2O7

The exploitation of ecofriendly luminescent materials is crucial for advancing phosphor applications. Herein, Eu3+ self-reduction was performed using the energy-saving high-temperature solid-phase method in air environment. Achieving controllable self-reduction is challenging for high-valent rare-earth and transition metal ions. Therefore, we incorporate charge compensators, such as Li+/K+ to control the reaction and obtain hetero-valent Eu2+/Eu3+. Experimental results indicate that charge compensators can eliminate vacancies, suppress self-reduction, and affect luminescence properties. Moreover, a nonequivalent substitution mechanism about self-reduction using a charge compensation model is discussed here. Notably, Eu2+ shows a strong blue narrow-band emission peak at 410 nm with a full width at half maxima of 34 nm, overlapping well with that of chlorophyll. The phosphors are nontoxic and exhibit high contrast under ultraviolet light, which can be utilized for forensic science detection. The precisely controllable self-reduction of phosphors can contribute to the development of next-generation smart and green materials. Advanced applications of the phosphors for plant growth, fingerprint visualization, and screen printing are also explored.