Bi$^{3+}$-doped Ba$_2$Y$_{1-x}$Lu$_x$NbO$_6$:Bi$^{3+}$ ($0 leq x leq 1.0$) solid solution phosphors: tunable photoluminescence and application for white LEDs

摘要

In this work, we use the conventional high temperature solid-state reaction to prepare Bi$^{3+}$-doped Ba$_2$Y$_{1-x}$Lu$_x$NbO$_6$:Bi$^{3+}$ ($0 leq x leq 1.0$) solid solution phosphors. To study the Lu$^{3+}$ content-dependent structural evolution and photoluminescence (PL) properties of the samples, the powder X-ray diffraction (pXRD), density functional theoretical (DFT) calculations, UV–visible diffuse reflectance and PL spectra are used. We find that all the phosphors are double-perovskite structural phase with a cubic space group of Fm$ar{3}$m, and the XRD positions shift to higher diffraction angle with the increase in Lu$^{3+}$ content. The emission positions of the samples tune from 447 to 493 nm, which are due to the crystal field modulation around the Bi3? ion. Among the obtained samples, the Ba$_2$Y$_{0.7}$Lu$_{0.3}$NbO$_6$:Bi$^{3+}$ shows the bestquantum efficiency (QE) of 57%. By using the optimal Ba$_2$Y$_{0.7}$Lu$_{0.3}$NbO$_6$:Bi$^{3+}$ solid solution phosphor, the red-emitting CaAlSiN:Eu$^{2+}$ phosphor, and a commercial 365 nm UV LED chip, we have fabricated a white LED device with the CIE coordinates at (0.378, 0.373), colour temperature (CT) of 3513 K, colour rendering index (CRI) of 67.1 and luminous efficiency of 39 lm W$^{-1}$.