Crystallization and up-conversion luminescence properties of Er3+/Yb3+-doped NaYF4-based nano-glass-ceramics

A crystallization study of Er3+/Yb3+-doped NaYF4-based nano-glass-ceramics and their optical characterisation is presented. NaYF4 nano-crystals were precipitated from heat treatments close to the glass transition temperature. The crystallization process occurs from a constant number of nuclei. The increase of dopant ions has a nucleating effect. Crystal growth is limited with the length of the heat treatment, keeping the crystal size to the nanometric scale. Er3+-single doped samples show a predominant green up-conversion emission under near infrared excitation at 980 nm, while a predominant red emission is observed in the Er3+/Yb3+ co-doped samples. The efficiency of the up-conversion emission is higher in the glass-ceramics than in the parent glasses.