Competitive absorption of Eu3+ and Tb3+codoped in NaGd(PO3)4 phosphors

The energy transfer efficiency from Gd3+ to Eu3+ is higher than that from Gd3+ to Tb3+ because there are less energy mismatches between the emission of Gd3+ and the absorption of Eu3+ than that between Gd3+ and Tb3+ in the host NaGd(PO3)4.