Role of Sensitizer Ions in Enhancing the Luminescence Intensity of Eu3+-Activated NaLa(MoO4)2 Phosphors and Judd–Ofelt Analysis for Solid-State Lighting and Temperature-Sensing Applications

Here, we report the effect of monovalent, divalent, and trivalent ions codoping on the luminescence and temperature-sensing properties of the NaLa(MoO4)2:Eu3+ phosphors. The phosphors were developed by a conventional solid-state synthesis at 750 °C/4 h. Structure refinement of the XRD data by the Rietveld method reveals that all the compounds are crystallized in nature with the tetragonal crystal structure and I41/a space group. The XPS results confirmed the oxidation state of Eu3+ and Mo6+ in the doped phosphors. The PL emission intensity increases with increasing Eu3+ content up to 11 mol . Further, an enhancement in the emission intensity by factors of 15.5, 1.4, and 1.6 is observed after the incorporation of Li+, Ca2+, and Bi3+ codopant ions, respectively, in NaLa(MoO4)2:Eu3+ (7 mol ). The Judd-Ofelt theory was used to compute the intensity parameters (Ω2, Ω4) and radiative properties, such as radiative lifetime (�rad), transition probabilities (AT), and branching ratio. A high activation energy of about 0.33 eV was obtained for the Li+-codoped NaLa(MoO4)2:Eu3+ phosphor, validating the high thermal stability of the phosphor. About 57 luminescence intensity was retained even at 423 K. The phosphors were also investigated for the temperature-sensing application by the fluorescence intensity ratio principle. The relative sensitivity was calculated for two different peak ratios. The maximum values of relative sensitivity at 300 K for I536/I590 and I536/I615 are 0.29 and 0.65 K-1, respectively. The CIE color coordinates lie in the red region, and the correlated color temperature values were observed between 1621 and 2314 K. Synthesized phosphors can act as promising multifunctional materials for the development of red components in solid-state lighting, laser applications, and noncontact optical temperature sensors. © 2024 American Chemical Society.