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

Abstract

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 ³P₀ → ³H₄ emission of Pr³⁺ weakened sharply upon the Pr³⁺–Ti⁴⁺ intervalence charge transfer (IVCT) excitation (λ_ex = 340 nm), whereas it was insensitive to temperature under the ³H₄ → ³P₂ excitation (λ_ex = 451 nm). Thus, the intensity ratio of the single ³P₀ emission at the two distinct excitation wavelengths (451 and 340 nm) could be exploited for optical thermometry. Excellent absolute sensing sensitivity (S_a-max = 1.74 K⁻¹), relative sensitivity (S_r-max = 3.64% K⁻¹) and thermal uncertainty (δT_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.