Positron annihilation spectroscopy and photoluminescence investigation of LaOF:Tb3+ nanophosphor fabricated via ultrasound assisted sonochemical route

Abstract LaOF:Tb 3+ nanophosphors were synthesized by modified sonochemical route using extracted Epigallocatechin gallate (EGCG) from green tea powder as surfactant. Powder X-ray diffraction patterns confirm the tetragonal phase of samples. Morphology of the products was tuned by changing the influential experimental parameters. Positron annihilation spectroscopy (PAS) was used to investigate the defect chemistry of the prepared samples. PAS specified the presence of defects at crystallite boundaries, vacancy clusters and large voids in the prepared compounds. Photoluminescence emission spectra consists of characteristic green emissions owing to 5 D 4  →  7 F J (J = 6, 5, 4, 3) transitions of Tb 3+ ions. The estimated critical distance between dopant ions was found to be ∼16.60 A is majorly responsible for the dipole-dipole interaction and concentration quenching. The photometric study such as Commission Internationale de L’Eclairage, Correlated Color Temperature and Color purity indicates that the obtained phosphors could be a promising green component for optoelectronic applications in particular to white LEDs.