Photoluminescence Properties and Thermometry Strategy in Anti‐Thermal‐Quenching Sm ³⁺ Single‐Doped Phosphate Phosphors

ABSTRACT Thermal quenching has long plagued rare‐earth‐doped luminescent materials as an inherent limitation, severely hampering their practical deployment in complex environments. Herein, novel orange‐red‐emitting K 3 Sc(PO 4 ) 2 :Sm 3+ phosphors with anti‐thermal quenching behavior have been successfully synthesized. The resultant samples have a trigonal crystal structure with space group P, where Sm 3+ ions occupied two distinct Sc 3+ lattice sites, inducing crystal field splitting and consequent emission peak splitting. The optimal doping concentration of Sm 3+ ions was determined to be 5 mol%, above which concentration quenching was dominated by electric dipole‐dipole interactions. Analysis of the intensity ratio between pure electric dipole and magnetic dipole transitions reveals that Sm 3+ ions are predominantly sited at the centrosymmetric 1a lattice position of Sc 3+ . Moreover, the stable octahedral framework endowed the phosphors with unique anti‐thermal quenching spectral properties, as evidenced by the integrated emission intensity at 573 K retaining 112.5% of its 298 K value. Finally, optical thermometric performance evaluated using emission transitions with distinct temperature dependencies underscores the phosphor's potential as a promising candidate for thermal sensing, thereby advancing the development of next‐generation luminescent thermometry platforms.