This paper reports the X-ray luminescence emission spectra of YTaO4 and GdT
aO4 activated by rare-earth ions. The luminescence efficiency of M'-type YT
aO4 activated by rare-earth ions was calculated. An assumption model was us
ed to explain the luminescent properties under X-ray excitation. The model
assumes that the TaO43- group absorbs all the excitation energy, then trans
fers part of the energy to rare-earth ions, followed by emission of rare-ea
rth ions. The calculation results agree with experimental results for M'-ty
pe YTaO4 activated by Sm3+, Tb3+, and Dy3+. M'-type YTaO4:Eu3+ is an except
ion because EU3+ may be involved in the process of energy absorption. (C) 2
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