Structural evolution-facilitated luminescence of Sm³⁺ in whitlockite-type phosphors with anti-thermal quenching behavior

Sm³⁺ luminescence has pivotal significance in the field of optoelectronics. However, their poor luminescence efficiency severely hinders their practical application as Sm³⁺-activated optical materials. Herein, two whitlockite-type phosphors, Sr₉Ln(PO₄)₇:Sm³⁺ (Ln = La and Y, marked as SLPO and SYPO), with anti-thermal quenching (ATQ) were reported. The substitution of La³⁺ with Y³⁺ results in structural evolution from the space group R $\overline{\mathbf{3}}$m of SLPO:Sm³⁺ to I2/a of SYPO:Sm³⁺, increasing the distance between Sm³⁺ dopants and suppressing nonradiative (NR) relaxation. The luminescence efficiency is significantly enhanced by 2.3 times. The representative SYPO:0.05Sm³⁺ phosphor demonstrates superior temperature sensing performance, achieving a relative sensitivity of 1.78%·K⁻¹, which exceeds the values reported for recently investigated Sm³⁺-activated phosphors. Moreover, the material is packaged in a 395 nm chip-excited white lighting source, resulting in a low correlated color temperature (CCT = 3394 K) with a high color rendering index (R_a = 97). This study provides a facile structural evolution strategy for designing highly efficient Sm³⁺-activated optical materials that facilitate wider applications.