Unveiling the Photoluminescence Properties and Thermal stability of Blue-Greenish to Green Light Emitting Tb-Doped NaBaBi(PO) Phosphors.

In this work, the solid-state reaction method was employed to synthesize NaBaBi(PO) (NBBP) and Tb doped NBBP samples under high temperature. X-ray diffraction confirmed phase formation, while SEM characterized surface morphology. Under the highest excitation at 378 nm, the emission spectra displayed peaks from the D and D levels, with the emission color shifting from bluish-green to green as the Tb concentration was varied. The reduction in D level emission and the increase in D level intensity with higher Tb concentration was due to the cross-relaxation process. The effect of Tb doping concentration on PL emission intensity indicates that the optimal concentration is 6 mol%. The estimated critical distance of approximately 20.487 Å suggests that multipole-multipole interactions primarily govern the concentration quenching effect. Thermal stability analysis showed that the phosphor retained 84% of its initial luminescence intensity at 483 K, demonstrating excellent resistance to thermal quenching. The measured average lifetime in the millisecond range further supports its potential for practical applications. Additionally, temperature-dependent lifetime analysis revealed a systematic variation in lifetime values with temperature, highlighting its suitability for temperature sensing applications. The CIE color coordinates, correlated color temperature (CCT), and color purity (CP) values were also reported, offering valuable insights into the colorimetric performance of Tb-doped NBBP phosphors. These findings are crucial for optimizing their application in solid-state lighting technologies.