Photoluminescent properties of (La _1-xY _x) _0.94Tb _0.06PO ₄ phosphor powders prepared by ultrasonic spray pyrolysis

The calculated crystallite sizes of (La _1-xV _x) _0.94Tb _0.06PO ₄ (0 ≤ × ≤1.0) phosphors ranged from 37-39 nm. Annealed (La _1-xY _x) _0.94Tb _0.06PO ₄ (0 ≤ × ≤1.0) phosphors showed a smooth, regular, and spherical morphology. Strong excitation peaks were appeared at 226 and 270 nm for all the phosphors. These were caused by the crystal splitting of ⁷D and ⁹D of 4f ⁷5pd ¹ configuration in Tb ³⁺, respectively. The characteristic emission peaks were observed at 489, 543, 585, and 621 nm, which were caused by the ⁵D ₄- ⁷F _j (j = 6-3) transitions of Tb ³⁺, respectively. The emission intensity at 543 nm increased with an increase in Y content up to 0.5 and then decreased for a higher Y content.