Concentration Dependence of Luminescent Properties for\({\text{Sr}}_{\mathbf{2}}{\text{TiO}}_{\mathbf{4}}\):$ {\text{Eu}}^{\mathbf{3}\mathbf{+}}$Red Phosphor and Its Charge Compensation

Abstract

Sr ₂TiO ₄:Eu ³⁺phosphors using M ⁺(M = Li ⁺, Na ⁺, and K ⁺) as charge compensators were prepared by the solid-state reaction. The powders were investigated by powder X-ray diffraction (XRD) and photoluminescence spectra (PL) to study the phase composition, structure, and luminescent properties. The results showed that Li ⁺ion was the best charge compensator. The phase was Sr ₂TiO ₄when the doping concentration was small ( $x\le 10.0$%). When $x$reached 15.0%, the phase turned into Sr ₃Ti ₃O ₇because of the structure damage. The phosphor could be effectively excited by ultraviolet (365, 395 nm) and blue light (465 nm), and thenitemitted intense red light that peaked at around 620 nm ( ⁵D ₀→ ⁷F ₂). In addition, the emission of 700 nm ( ⁵D ₀→ ⁷F ₄) enhanced the red light color purity. The CIE chromaticity coordinates of samples with the higher red emission were between (0.650, 0.344) and (0.635, 0.352). Doped layered titanate Sr ₂TiO ₄:Eu ³⁺is a promising candidate red phosphor for white LEDs which can be suited for both near-UV LED chip and blue LED chip.