Anomalous thermal quenching behavior of novel orange-red SrLa_1-xNaTeO₆:xSm³⁺ phosphors for optical temperature sensing

A series of novel orange-red phosphors were synthesized in this study by adding Sm3+ into the double perovskitestructured SrLaNaTeO6 host lattice using a solid-state reaction technique, and their luminescence properties and thermal stability were studied in detail. X-ray diffraction (XRD) analyses revealed that the obtained SrLa1-xNaTeO6:xSm(3+) phosphors are triclinically symmetrical, with a space group of Fm-3m. The optimal Sm3+ doping concentration was determined to be x = 0.05 in the SrLa1-xNaTeO6:xSm(3+) phosphor, and excessive dopants will cause concentration quenching due to energy transfer interaction between Sm3+ ions. Under the excitation of near-ultraviolet lambda(ex) = 405 nm, the luminous intensity of SrLa0 & sdot;95NaTeO6:0.05Sm(3+) phosphor at 573 K remained at 125.8% of its original value at 298 K. And then, the phosphor has excellent quantum yield (49.26%) and negative thermal quenching. Besides, the optimum SA and SR values of SrLa0 & sdot;95NaTeO6:0.05Sm(3+) phosphor were 0.088% K-1@573 K (SA) and 0.149% K-1@498 K (SR), respectively. The excellent negative thermal quenching and good thermal stability of SrLa0 & sdot;95NaTeO6:0.05Sm(3+) phosphor indicate that it has a potential for applications as white LEDs and optical temperature sensing.