Single band ratiometric luminescence thermometry based on Pr3+ doped oxides containing charge transfer states

Luminescence thermometry, an important technique for remote temperature readout, requires the exploitation of new thermometric strategies to improve sensing properties. Herein, we propose a novel single band ratiometric thermometric strategy based on the dependence of luminescence thermal quenching behavior on the excitation wavelength in a Pr3+:Gd2ZnTiO6 phosphor. With the increase of temperature, the P-3(0) -> H-3(4) emission of Pr3+ weakened sharply upon the Pr3+-Ti4+ intervalence charge transfer (IVCT) excitation (lambda(ex) = 340 nm), whereas it was insensitive to temperature under the H-3(4) -> P-3(2) excitation (lambda(ex) = 451 nm). Thus, the intensity ratio of the single P-3(0) emission at the two distinct excitation wavelengths (451 and 340 nm) could be exploited for optical thermometry. Excellent absolute sensing sensitivity (Sa-max = 1.74 K-1), relative sensitivity (Sr-max = 3.64% K-1) and thermal uncertainty (delta T-min = 0.14 K) were realized, which were superior to those of many other thermometric phosphors. This strategy was proved to be also valid for other Pr3+ doped oxides containing IVCT states, such as Pr3+:Gd2MgTiO6, Pr3+:LiLaMgWO6 and Pr3+:La2ZnTiO6. These results could provide useful information for developing innovative luminescent thermometers with high performance.