Synthesis, Photoluminescent Characteristics and Eu-Induced Phase Transitions in SrZrO:Eu 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 SrZrO (cubic) to the SrZrO (orthorhombic) phase was observed, and the impact of the occupied sites of Eu ions on the lifetime of SrZrO: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 SrZrO 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 SrZrO: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.