Design and synthesis of a novel blue-emitting CaNaSb₂O₆F:Bi³⁺ phosphor for optical temperature sensing

Bi³⁺ has gained increasing attention due to its abundant reserves, adjustable luminous colour and high chemical stability, therefore, Bi³⁺-activated luminescent materials have already been extensively applied in various fields. Herein, a novel blue-emitting CaNaSb₂O₆F:Bi³⁺ (CNSOF:Bi³⁺) phosphor with a pyrochlore-type structure with the space group Fd3̄m (277) was successfully synthesized. It exhibits a broad absorption band in the n-UV region (290-390 nm) and an ideal blue emission band centered at 441 nm. Interestingly, the wide emission peak of CNSOF:Bi³⁺ shows strongly temperature-dependent fluorescence properties and good thermal degradation resistance in the cycle temperature range from 298 K to 473 K, and the relative sensitivity is calculated to reach the maximum value of 2.34% K^-1 at 423 K. Besides, the phosphor is different from a traditional optical temperature sensing material which shows the emission peak of trivalent rare earth ions. The wide emission peak makes the instrument insensitive to the peak shift, which dramatically reduces the requirement of the instrument, and the emission peak does not shift with the temperature to enhance the measurement stability, thus saving the cost. These results indicate that the CNSOF:Bi³⁺ blue emitting phosphor has potential applications in temperature sensing.