Studies of Radiation-Induced Defects in Li2SiO3:Sm Phosphor Material

Li2SiO3:Sm was synthesized by the solution combustion method. Powder x-ray diffraction technique was used to find the phase formation. Li2SiO3:Sm exhibits thermoluminescence (TL) peaks at approximately 140 degrees C, 155 degrees C, 190 degrees C, 250 degrees C, and 405 degrees C. Three defect centers contribute to the observed electron spin resonance spectrum from the gamma irradiated phosphor. Center I with principal g-values g(parallel to) = 2.0206 and g(perpendicular to) = 2.0028 is identified as an O-2(-) ion while center II, with an isotropic g-factor 2.0039, is assigned to an F+-type center. Center III is assigned to a Ti3+ center. The Ti3+ center is related to the 250 degrees C TL peak while the O-2(-) ion also correlates with the main TL peak at 250 degrees C. An additional defect center is observed during thermal annealing experiments, and the center (assigned to F+ center) seems to originate from an F center. The F center appears to be associated with the high temperature TL peak in a Li2SiO3: Sm phosphor. The luminescence spectrum reveals the dominant emission peaks at 605 ((4)G(5/2) -> H-6(7/2)) nm under the excitation wavelength of 402 nm.