Luminescence from the Pr3+ 4f15d1 and 1S0 states in LiLaP4O12

The photoluminescence and excitation spectra of Pr3+ activated LiLaP4O12 has been investigated in the 10–300 K temperature region. At all temperatures, the luminescence consists of optical transitions emanating from both the Pr3+ 4f15d1 and the 1S0 states. However, at low temperatures the emission spectrum is dominated by the intraconfiguration emission transitions emanating from the Pr3+ 1S0 state. With increasing temperature, there is an exchange of intensity between the two emitting states; emission transitions from the 1S0 state exhibit strong intensity quenching while the 4f15d1→4f2 emission transitions reveal intensity gain. These results are explained on the basis of thermal population of the 4f15d1 state by the 1S0 state. The energy barrier of 0.05 eV (403 cm−1) for the nonradiative process is determined from the temperature dependence of the 1S0 lifetime.