Luminescent ratiometric temperature sensing based on Pr³⁺ and Bi³⁺ co-doped CaNb₂O₆ phosphors

The ratiometric luminescent thermometry based on dual-emission centers can effectively overcome the limita-tions of temperature sensing based on thermally coupled levels. Herein, Bi3+ and Pr3+ co-doped CaNb2O6 phosphors were prepared by high-temperature solid-phase reactions, and crystal structural and photo-luminescence were characterized. Then the luminescent thermometric properties of the obtained samples were studied, and the maximum absolute and relative sensitivity of the optimal sample (CaNb2O6: 0.5%Bi3+/0.5%Pr3+ phosphor) achieved are 0.09 K-1 @ 528 K and 2.17 % K-1 @ 453 K, respectively. Furthermore, the luminescence of CaNb2O6: 0.5%Bi3+/0.5%Pr3+ phosphor transforms remarkably from blue to red as the temperature rises, which can be adopted to monitor the ambient temperature via the glow color of the phosphor. To sum up, Bi3+ and Pr3+ co-doped CaNb2O6 phosphors have been shown to have good thermosensitive and thermochromic characteristics.