The emission and excitation properties of a SrB 4 O 7 :1% Pr 3+ powder sample and a Sr 0.7 La 0.3 Al 11.7 Mg 0.3 O 19 :3.5% Pr 3+ single crystal were investigated using x-ray and synchrotron radiation. The 4f5d states of Pr 3+ in these host lattices are at a higher energy than the 4f 2 [ 1 S 0 ] state. In the hexa-aluminate this results in the successive emission of two photons. 1 S 0 → 1 I 6 emission is followed by emission from the 3 P 0 state. The quantum efficiency of the total 3 P 0 emission is 25%. In the tetra-borate the 3 P 0 emission is quenched by multiphonon relaxation to the 1 D 2 state from which only weak emission is observed. In the hexa-aluminate as in the tetra-borate, host lattice excitation does not result in efficient emission from the 1 S 0 state. In the hexa-aluminate the excitation energy is transferred from the host lattice preferentially to the lower-energy 3 P J and 1 I 6 states, resulting in 3 P 0 emission only.
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Kolk et al. (2001) studied this question.
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