Ortho-vanadates K3RE(VO4)2 (RE = La, Pr, Eu, Gd, Dy, Y) for near UV-converted phosphors

Abstract

The orthovanadate poly-crystals K3RE(VO4)2 (RE = La, Pr, Eu, Gd, Dy, Y) were synthesized via the solid-state reaction route. The crystal phase formation was verified through X-ray diffraction (XRD) studies and was performed by structural refinements. The optical properties were also investigated in detail. K3RE(VO4)2 (RE = Eu, Dy, Gd, Pr, La, Y) phosphors present different luminescence behaviors: the profiles of excitation and emission spectra, the spectra shift, the luminescence decay lifetimes, the absolute quantum efficiency (QE), and the CIE color coordinates are very different. The luminescence of K3RE(VO4)2 (RE = La, Gd, Y, Pr) presents yellow or yellowish green color, while, K3Dy(VO4)2 and K3Eu(VO4)2 show white and red luminescence, respectively. This was discussed on the base of the different micro-structure, activator centers, and the charge transfer transitions from [VO4]3− groups in the lattices. K3Y(VO4)2 and K3Eu(VO4)2 show higher QE values of 47.0% and 45.0% at room temperature, respectively. All the phosphors have efficient absorption in the region of near-UV wavelengths or blue wavelength region. This can well match with the light from UV-LED (360–400 nm) or blue LED chips (450–480 nm) based on GaN semiconductor. K3RE(VO4)2 could be suggested to be a potential candidate to give further investigations for the application on near-UV excited white LEDs.