Direct imaging of inhomogeneous distribution of Er3 + ions in lead fluoride nanocrystals

Er3 +-doped lead fluoride nanocrystals (NCs) were precipitated in glasses by heat treatment at 490 °C, and the distribution of Er3 + ions inside the NCs was investigated using electron energy loss spectroscopy. Nucleation started with the formation of 2–4-nm-diameter NCs highly enriched in Er3 +. With further heat treatment, NCs with inhomogeneous Er3 + distribution grew. Crystal structure in individual fluoride NCs changed from tetragonal to cubic due to the variation in Er3 + concentration.

► PbErF5 nanocrystals formed as the initial phase in oxyfluoride glass-ceramics. ► Growth of these initial phase led to the formation of Pb1–xErxF5 (x < 0.5) nanocrystal on top. ► HR-TEM image and electron diffraction pattern evidenced that nanocrystals were not pure phase. ► EELS evidenced inhomogeneous distribution of Er3 + ions in the lead fluoride nanocrystals.