Luminescence of Ca(NbO3)2:Pr3+: Pr3+ and self-trapped exciton emission

Abstract Photoluminescence and time resolved photoluminescence spectra of Ca(NbO 3 ) 2 doped with Pr 3+ , excited under 37,000 cm −1 (270 nm), obtained at high hydrostatic pressure up to 20 kbar applied in a sapphire anvil cells, are presented. At ambient conditions, the emission spectrum obtained in the time interval 0–1 μs is dominated by spin allowed transitions from the 3 P 0 state. The luminescence related to transitions from 1 D 2 , characterized by a decay time equal to 33 μs, is observed when one excites directly the Pr 3+ ion with 30,770 cm −1 (325 nm) wavelength. The introduction of Pr 3+ impurities in Ca(NbO 3 ) 2 does not quench the self-trapped exciton (STE) luminescence. This luminescence, peaking at 20,000 cm −1 (500 nm), having a decay time of 61 ± 1 μs, still occurs when the crystal is excited with a wavelength of 37,000 cm −1 (270 nm) or shorter. Under such excitation a fraction of the STE luminescence is reabsorbed by Pr 3+ ions; in this case the emission lifetime of the 1 D 2 → 3 H 4 transition of Pr 3+ is 64 ± 3 μs. This effect is stable also at high pressure.