The influence of the Pr3+ 4f15d1 configuration on the 1S0 emission efficiency and lifetime in LaPO4

The photoluminescence and excitation spectra of Pr3+ activated LaPO4 has been investigated in the 1.6-300 K temperature region. At room temperature, the luminescence of LaPO4:Pr3+ is composed of the interconfigurational 4f15d1 → 4f2 emission transitions. However, in the 1.6-60 K temperature range, the emission spectrum also consists of the intraconfigurational emission transitions that emanate from the 1S0 state. A radiative lifetime of 145 ns is measured for the Pr3+1S0 → 1I6 emission transition in LaPO4. This is one of the shortest radiative lifetime observed for this transition in a solid. The energy position of the Pr3+1S0 state in LaPO4 is established by high-resolution emission spectrum at 46 375 ± 5 cm−1. A detailed analysis of the thermal quenching of the 1S0 lifetime and emission intensity is presented. It is proposed that the lowest energy state of the relaxed 4f15d1 configuration is situated energetically below that of the 1S0 state.