Synthesis, Photoluminescent Characteristics and Eu 3+ -Induced Phase Transitions in Sr 3 Zr 2 O 7 :Eu 3+ Red Phosphors

Designing phosphors that are excited by blue light is extraordinarily important for white light-emitting diodes (w-LEDs). In the present study, a new Ruddlesden-Popper type of SZO: Eu ( = 0.01~0.10) phosphors was developed using solid-state reactions. Interestingly, a Eu doping-induced phase transformation from the Sr Zr O (cubic) to the SrZrO (orthorhombic) phase was observed, and the impact of the occupied sites of Eu ions on the lifetime of Sr Zr O : Eu phosphors is discussed in detail. Diffuse reflectance spectroscopy results showed that the band gap of SZO: Eu phosphors gradually increased from 3.48 eV for undoped Sr Zr O hosts to 3.67 eV for SZO:0.10Eu samples. The fluorescence excitation spectrum showed that ultraviolet (300 nm), near-ultraviolet (396 nm) and blue light (464 nm) were all effective excitation pump sources of Sr Zr O : Eu phosphors, and the strongest emission at 615 nm originated from an electric dipole transition ( D → F ). CIE coordinates moved from orange (0.5969, 0.4267) to the reddish-orange region (0.6155, 0.3827), and the color purity also increased. The fabricated w-LED was placed on a 460 nm chip with a mixture of YAG:Ce and SZO:0.1Eu samples and showed "warm" white light with a color rendering index (CRI) of 81.8 and a correlation color temperature (CCT) of 5386 K, indicating great potential for application in blue chip white LEDs.