Structure and Luminescence of New Red-Emitting Materials-Eu³⁺-Doped Triple Orthovanadates NaALa(VO₄)₂ (A = Ca, Sr, Ba)

The new red-emitting phosphors of Eu³⁺-doped triple orthovanadates NaALa(VO₄)₂ (A = Ca, Sr, Ba) were prepared by the high-temperature solid-state reaction. The formation of single phase compound with isostructural structure of Ba₃(VO₄)₂ was verified through X-ray diffraction (XRD) studies. The photoluminescence excitation and emission spectra, the fluorescence decay curves and the dependence of luminescence intensity on doping level were investigated. The phosphor can be efficiently excited by near UV and blue light to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition ⁵D₀→⁷F₂ of Eu³⁺ ions. Their potential applications as red-emitting phosphors for solid-state lighting were evaluated in comparison with the Eu³⁺-doped lanthanum orthovanadate LaVO₄ and other reported references. The luminescence was discussed in detail on the base of the crystal structures. The luminescence thermal stability on temperature was investigated and the thermal activated energy was calculated. The phosphors can be suggested to be a potential red-emitting phosphor for the application on white LEDs under irradiation of near-UV or blue chips.