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Spectroscopic studies of Tm-doped zirconia nanoparticles



Intra-4f12 transitions of Tm3+ ions in zirconia powders processed by solution combustion synthesis (CS) were studied by optical techniques. The results were compared with the ones obtained in reference samples of yttria stabilized zirconia fibers grown by laser floating zone. The spectroscopic features observed for the tetragonal fibre were compared with the Stark lines detected in the polyphasic (monoclinic and tetragonal) powder suggesting additional Tm3+ sites/environments due to the ions in the monoclinic host. The stability of the blue 1D2 → 3F4 and red 1G4 → 3H6 transitions was found to be strongly dependent on temperature. For the fibres, the blue luminescence increases by a factor of two between 15 K and the room temperature when pumping the sample in the 1D2 level. When the excitation is performed in the 1G4 state a higher stability of the red luminescence was found to occur in fibres than in the polyphasic powder. Constant 1G4 → 3H6 integrated intensity was observed in the fibres, while a decrease of the red luminescence efficiency occurs with temperature for the polyphasic powder. The suppression of the nonradiative paths which compete with the radiative transition could be attained by using thulium doped yttria stabilized CS powders.