Structural and spectroscopic properties of Nd³⁺: Y ₂Si₂O₇ phosphors

Phosphors of α-Y₂Si₂O₇ doped with Nd³⁺ ions were prepared using the sol-gel technique. Nano-sized crystalline phosphor powders were obtained by annealing the dried gels at 960 °C. The crystallization properties of the phosphor powders were determined from their XRD patterns. The α-Y₂Si₂O₇ phase was the only phase observed in all compositions. As the amount of amorphous SiO₂ in the composition was increased, the crystalline sizes and the widths of the size distribution curves were found to decrease from 17.8 nm to 10.6 nm and from 15.6 nm to 12.2 nm, respectively. The spectroscopic properties of the powders were studied by measuring the luminescence and the decay patterns of the ⁴F_3/2→ ⁴I _9/2 and ⁴F_3/2→ ⁴I _11/2 transitions between 50 K and 310 K. No appreciable effect of the crystallite sizes on the average lifetime of the ⁴F_3/2 level was observed at temperatures below 100 K. The effect of temperature, however, becomes relevant above 100 K as the size of α-Y ₂Si₂O₇ nano-crystal becomes smaller.