Reversible luminescence modulation and temperature‐sensing properties of Pr 3+ /Yb 3+ codoped K 0.5 Na 0.5 NbO 3 ceramics

In this work, we have prepared a novel (K 0.5 Na 0.5 ) 0.99‐ x Pr x Yb 0.01 NbO 3 (abbreviated as KNN: x Pr 3+ /0.01Yb 3+ , x = 0.0006, 0.0008, 0.001, 0.002, 0.003, and 0.004) ceramics, which possess visible UC emissions, photochromic (PC) and optical thermometric properties. Under the excitation of a 980‐nm diode laser, all the samples show the featured emissions of Pr 3+ ions and the UC emission intensity is greatly dependent on the Pr 3+ doping content. The optimal UC luminescence intensity is obtained at x = 0.001. All the prepared samples show a strong PC reaction, and a large luminescence quenching degree (ΔR t ) of 74.94% is found. The optical thermometric properties of both the irradiated and unirradiated KNN:0.001Pr 3+ /0.01Yb 3+ ceramics in the temperature range of 123‐573 K have been investigated via measuring the temperature‐dependent UC emission spectra of green emissions, which originate from the two 3 P 1 and 3 P 0 thermally coupled levels. It has been found that the prepared samples have both excellent PC behaviors and temperature‐sensing performances. These results suggest that the KNN: x Pr 3+ /0.01Yb 3+ ceramics are promising candidates for the applications in PC reaction and thermometers.