Re-determination of the crystal structure of Ca2Y8Si6O26 and study on the luminescent properties of Ca2Y8Si6O26:Tb3+

The crystal structure of silicate oxyapatite Ca2Y8Si6O26 was indexed as hexagonal, space group P63/m, α=0.93515 nm, c=0.67872 nm, α=β=90°, γ=120°, V=0.5138692 nm3. Three strong peaks located at 32.079°, 32.595°, and 50.104° with d=2.7903, 2.74649, 1.8194 was in accordance with (211), (112), and (213) planes. The optimum concentration of Tb3+ in Ca2Y8Si6O26 to yield highest photoluminescence intensity was 10 mol.% of Y3+. The corresponding excitation spectrum consisted of an intense broad band from 220 to 260 nm. The photoluminescence measurements showed that the green emission originated from 5D4−7F5 was predominant in the measured range with strong doublet lines at 543 and 549 nm.