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: x Eu 3+ ( x = 0.01~0.10) phosphors was developed using solid-state reactions. Interestingly, a Eu 3+ doping-induced phase transformation from the Sr 3 Zr 2 O 7 (cubic) to the SrZrO 3 (orthorhombic) phase was observed, and the impact of the occupied sites of Eu 3+ ions on the lifetime of Sr 3 Zr 2 O 7 : x Eu 3+ phosphors is discussed in detail. Diffuse reflectance spectroscopy results showed that the band gap of SZO: x Eu 3+ phosphors gradually increased from 3.48 eV for undoped Sr 3 Zr 2 O 7 hosts to 3.67 eV for SZO:0.10Eu 3+ 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 3 Zr 2 O 7 : x Eu 3+ phosphors, and the strongest emission at 615 nm originated from an electric dipole transition ( 5 D 0 → 7 F 2 ). 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 3+ and SZO:0.1Eu 3+ 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.