Figure 5

(a–c) SEM images of 5% Er3+-doped La2O2S nanocrystals calcined under CS2/CO atmosphere at (a) 700 °C, (b) 800 °C and (c) 900 °C, respectively. (d–f) SEM images of 5% Er3+-doped La2O2SO4 nanocrystals annealed under air flow at (d) 700 °C, (e) 800 °C and (f) 900 °C, respectively. (g) Schematic of morphology evolution with increasing annealing temperature in Er3+-doped La2O2S.