Crystal Structure and Luminescent Properties of Sr ₂ SiO ₄ :Eu ²⁺ Phosphor Prepared by Sol-Gel Method

Motivation A series of Eu ²⁺ (0.0025≤ × ≤0.025) activated Sr ₂ SiO ₄ :xEu ²⁺ (SSO:xEu ²⁺ ) phosphors were synthesized via a sol-gel method. The phosphors were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. The differences between α’ and β phase of SSO in the density of states and energy band gap were investigated. Results The energy gap of α’-SSO and β-SSO are 4.489 and 4.106 eV, respectively. While, two samples showed similar total and partial densities of states. Under the excitation by the ultra violet (UV) light (365 nm), the SSO:xEu ²⁺ phosphor exhibited a green emission band from 400 to 700 nm, which was corresponding to the transition of 5 d → 4 f of Eu ²⁺ ions. Two emission peaks at 464 and 532 nm could be obtained through Gauss fitting curves. The ratio of the blue to green emission peak decreased with the Eu ²⁺ concentration and the peaks shifted regularly with it. The thermal quenching property was investigated and its activation energy was calculated. The results indicated that this phosphor could be a candidate of green phosphor for UV-based light-emitting diodes (LEDs).