High pressure luminescence of Nd³⁺ in YAlO₃ perovskite nanocrystals: A crystal-field analysis

Pressure-induced energy blue- and red-shifts of the ⁴F_3/2 → ⁴I_9/2,11/2 near-infrared emission lines of Nd³⁺ ions in YAlO₃ perovskite nano-particles have been measured from ambient conditions up to 29 GPa. Different positive and negative linear pressure coefficients have been calibrated for the emission lines and related to pressure-induced changes in the interactions between those Nd³⁺ ions and their twelve oxygen ligands at the yttrium site. Potentiality of the simple overlap model, combined with ab initio structural calculations, in the description of the effects of these interactions on the energy levels and luminescence properties of the optically active Nd³⁺ ion is emphasized. Simulations show how the energies of the 4f³ ground configuration and the barycenters of the multiplets increase with pressure, whereas the Coulomb interaction between f-electrons decreases and the crystal-field strength increases. All these effects combined explain the wavelength blue-shifts of some near-infrared emission lines of Nd³⁺ ions. Large pressure rates of various emission lines suggest that a YAlO₃ perovskite nano-crystal can be a potential candidate for near-infrared optical pressure sensors.