Near-infrared emission in Na$_5$Y(WO$_4$)$_4$ : Nd$^{3+}$

Luminescence in Na$_5$Y(WO$_4$)$_4$ : Nd$^{3+}$ is investigated for the first time. The emission is in the near-infrared region. The well-known $^4F_{3/2}\to{}^4I_{9/2}$ transition leads to most intense line at 1069 nm. The excitation and emission spectra are interpreted using the energy level diagram of Nd$^{3+}$. The excitation spectrum is made up of a large number of sharp lines attributable to various $f$–$f$ transitions. A weak band at 360 nm in the excitation spectrum is assigned to the host. Notwithstanding large Y–Y distances, the luminescence is quenched at concentrations exceeding 2 mol.%. The critical distance for energy transfer among Nd$^{3+}$ ions is found to be 32.85 $\mathring{\mathrm{A}}$.