Luminescence of Ca(NbO3)2:Pr3+ at ambient and high hydrostatic pressure

In this contribution, photoluminescence and time-resolved photoluminescence spectra of Ca(NbO3)2 doped with Pr3+ obtained at high hydrostatic pressure up to 72 kbar applied in a diamond anvil cell are presented. At ambient conditions, the emission spectrum obtained in the time interval 0-1 μs is dominated by spin-allowed transitions from the 3P0 state. On the other hand, transitions from 1D2, characterized by a decay time equal to 30 μs dominate the steady-state luminescence. At pressures lower than 60 kbar, the continuous wave emission spectrum consists of sharp lines peaking between 600 and 625 nm, related to the 1D2→3H4 transition and three lines at 500, 550 and 650 nm related to emission transitions originating from the 3P0 level of Pr3+. The emission from the 1D2 excited state depends weakly on the pressure. Its decay time decreases from 33 μs at ambient pressure to less than 22 μs at 68 kbar. On the other hand, the 3P0 emission is strongly pressure dependent. At pressures of 60 kbar and higher, the Pr3+ emission intensity from the 3P0 state decreases. This is accompanied by a strong shortening of the luminescence decay time. The observed pressure quenching of the f-f emission transitions and the concomitant lifetime shortening have been attributed to increasing crossover from the 3P0 state of Pr3+ to a Pr3+-trapped exciton state.