Effects of 6 MeV energy electrons on lattice parameters of CaSO4:Eu nanophosphor

Nanorods of CaSO4:Eu were prepared by chemical co-precipitation method which further annealed and quenched in a quartz crucible at 650 °C for 2 h in air. The average grain size of the nanophosphor was calculated using Scherrer’s formula and estimated to be around 40 nm for as synthesized and 80 nm for annealed sample, which confirms its nanocrystalline form. XRD analysis reveals that CaSO4:Eu changes its phase from hexagonal to orthorhombic because of annealing treatment. TEM image shows that there is change in the morphology of the nanocrystallites if it is annealed at 650 °C. The doped Eu3+ ion is present as a substitutional impurity in the host phosphor. As synthesized and annealed CaSO4:Eu powder was irradiated by 6 MeV energy electrons for different fluences varying from 1.5×1015 e/cm2 to 4.5×1015 e/cm2. The lattice parameters of as-synthesized and annealed CaSO4:Eu were found to be decreased with increase in the electron fluence. The ratio of the positive charge to the ionic radius of Eu3+ is much larger than that of Ca2+ and a part of substituted Eu3+ is reduced to Eu2+ by capturing an electron during irradiation and therefore, the lattice parameters of phosphor decreases with increase in the electron fluence.