Characterization and luminescence properties of sol–gel derived M′-type LuTaO4:Ln3+ (Ln = Pr, Sm, Dy) phosphors

M′-type Lu1−xLnxTaO4 (Ln = Pr, Sm, Dy) phosphors have been successfully synthesized by sol–gel technique, their crystallization, morphology, photoluminescence and X-ray excited luminescence properties were investigated in detail. The phosphors had good crystallization behavior. The optimum doping concentrations of Pr3+, Sm3+ and Dy3+ in LuTaO4 were at x = 0.003, 0.025, 0.02, respectively. They exhibited a more efficient host excitation relative to the 4f–4f excitations of the rare-earth ions, and a dominant 1D2 → 3H4, 4G5/2 → 6H7/2 or 4F9/2 → 6H13/2 emission for Pr3+, Sm3+ or Dy3+, respectively, which corresponds to the average decay time of 21.7, 745.7 or 10.0 μs, respectively. It is expected that Pr3+- or Dy3+-doped LuTaO4 phosphors with a microsecond level decay time are very encouraging for applications in X-ray computerized tomographic imaging with high spatial resolution.