Photoluminescence and energy transfer in Eu 3+ ‐doped alkali gadolinium phosphates

Spectral‐kinetic characteristics of the undoped and Eu 3+ ‐doped alkali gadolinium phosphates of the type of MGdP 4 O 12 (M = Li, Na) have been studied within the 4.2–300 K temperature range using time‐resolved luminescence spectroscopy techniques. The photon cascade luminescence of Gd 3+ ions in the undoped LiGdP 4 O 12 phosphate has been observed. In the case of the Eu 3+ ‐doped MGdP 4 O 12 phosphates, no quantum cutting process takes place due to the spectral overlap of the charge transfer band of Eu 3+ with the bands arising from the 6 G J levels of Gd 3+ . The processes of energy migration along the Gd 3+ sublattice and the Gd 3+  → Eu 3+ energy transfer have been studied. The phonon‐assisted population of the Gd 3+ 6 P 5/2,3/2 excited levels is suggested to be responsible for the increase in the probability of the energy migration along the Gd 3+ sublattice via the 6 P J states with the subsequent energy transfer to the 5 I J levels of an Eu 3+ ion.