Temperature and Eu2+-Doping Induced Phase Selection in NaAlSiO4 Polymorphs and the Controlled Yellow/Blue Emission

The union of temperature-dependent phase transition and relating structural transformation via modification of chemical compositions is of fundamental importance for the discovery of new materials or their functional properties optimization. Herein, the synthesis temperature and Eu²⁺-doping content induced phase selection and variations of the local structures in nepheline, low-carnegieite and high-carnegieite types of NaAlSiO₄ polymorphs were studied in detail. The luminescence of Eu²⁺ in low-carnegieite and nepheline phases shows blue (460 nm) and yellow (540 nm) broad-band emissions, respectively, under near-ultraviolet excitation. The photoluminescence evolution can be triggered by the different synthesis temperatures in relation to the Eu²⁺-doping concentration, as corroborated by density functional theory calculations on the local coordination structures and corresponding mechanical stabilities in terms of the Debye temperature. The fabricated white light-emitting diode device with high color rendering index demonstrates that the multicolor phosphors from one system provides a new gateway for the photoluminescence tuning.