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 mu s is dominated by spin-allowed transitions from the P-3(0) state. On the other hand, transitions from D-1(2), characterized by a decay time equal to 30 mu s 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 D-1(2) -> H-3(4) transition and three lines at 500, 550 and 650 nm related to emission transitions originating from the P-3(0) level of Pr3+. The emission from the D-1(2) excited state depends weakly on the pressure. Its decay time decreases from 33 mu s at ambient pressure to less than 22 Its at 68 kbar. On the other hand, the P-3(0) emission is strongly pressure dependent, At pressures of 60 kbar and higher, the Pr3+ emission intensity from the P-3(0) 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 P-3(0) state of Pr3+ to a Pr3+-trapped exciton stat