High pressure luminescence of Nd in YAlO perovskite nanocrystals: A crystal-field analysis.

Pressure-induced energy blue- and red-shifts of the F → I near-infrared emission lines of Nd ions in YAlO 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 Nd 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 Nd ion is emphasized. Simulations show how the energies of the 4f 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 Nd ions. Large pressure rates of various emission lines suggest that a YAlO perovskite nano-crystal can be a potential candidate for near-infrared optical pressure sensors.