High moisture resistant and thermal stable NaYSiO₄:Eu³⁺ red phosphor with activator protected by cyclic silicon-oxygen tetrahedra

The stability of phosphors and matrix under humid conditions and elevated temperatures is essential for the stable performance of light-emitting diodes. We synthesized a series of NaYSiO4:xEu(3+) (x = 0.00-0.14) phosphors via a sol -gel reaction. The NaYSiO4 crystallizes in a hexagonal structure (space group P63/m) with a bandgap value of 4.60 eV. In this lattice, doped Eu3+ occupied the center of non-inversion symmetry. Under the optimal 394 nm excitation, the NaYSiO4:0.04Eu(3+) sample showed a strong red emission at 618 nm with a high color purity of up to 94.98 %. Impressively, it exhibited high thermal stability (523 K, > 50 %, Delta E = 0.24089 eV) and moisture resistance. Due to the protection of the stable coordination environment provided by cyclic Si -O -Si bands and strong binding energy, it retained 90.2 % of its original intensity after exposure under the relative humidity of 85 % at 85 degrees C for 240 h. Furthermore, this red phosphor was packaged into a cold white lightemitting diode with Commission International de l ' Eclairage (0.3250, 0.3364). From the perspective of host lattice structure, this work provides a new strategy to withstand luminous degradation under humid and warm conditions.