Charge transfer band excitation of La3NbO7:Sm3+ phosphors induced abnormal thermal quenching toward high‐sensitivity thermometers

Abstract Different luminescent behaviors of La 3 NbO 7 :Sm 3+ phosphors under the excitations of charge transfer band (CTB, 250 nm) and featured absorption peak ( 6 H 5/2 → 4 H 7/2 , 405 nm) of Sm 3+ ions were demonstrated. Under the excitation wavelength of 405 nm, the optimal La 3 NbO 7 :0.1Sm 3+ phosphor exhibited an orange‐red emission while the chromatic coordinate was found to be (0.609, 0.387), which also showed the excellent thermal performance, exhibiting its emission intensity of about 90.67% at 423 K with respect to 303 K. In the case of CTB excitation, the La 3 NbO 7 :0.1Sm 3+ phosphor emitted an orange‐yellow region with the chromaticity coordinate of (0.540, 0.443), and the emission intensity was stronger than the above one ( λ ex =405 nm) even though the optimized sample would be changed to the La 3 NbO 7 :0.05Sm 3+ phosphor. With the increase of temperature, the obtained sample revealed an abnormal thermal quenching phenomenon between the emission peak of the host material and the emission transition of 4 G 5/2 → 6 H 9/2 under the excitation wavelength of 250 nm, which could be suggested to turn into a pair of thermal‐couple levels. Therefore, the sensing sensitivity of the obtained sample was further investigated based on the fluorescence intensity ratio theory. Eventually, the absolute and relative sensing sensitivities of the La 3 NbO 7 :0.01Sm 3+ phosphor were estimated to be as high as 5.379 × 10 −2 K −1 and 1.60% K −1 , respectively.