Thermal stable NaMgLaTeO6:Dy3+ double perovskite yellow phosphors for w-LEDs and latent fingerprint visualization

The novel Dy³⁺-doped NaMgLaTeO₆ (NaMgLaTeO₆:Dy³⁺) phosphors were produced through a high-temperature solid-state reaction. X-ray diffraction (XRD) analysis and Rietveld refinement manifest that the pure phosphor was committed to the space group (P2_1/m (11)) and features the double perovskite structure. The band gap (E_g) of the direct semiconductor NaMgLaTeO₆ is calculated to be 2.065 eV. Under 388 nm excitation, the ⁴F_9/2→⁶H_13/2 energy level transition contributes to the maximum emission peak at 572 nm. Other properties of the phosphor include optimal concentration (x = 5 mol %), high thermal stability, activation energy (E_a = 0.31 eV), and internal quantum efficiency (IQE = 31.44 %). The relevant color coordinate of the white light emitting diode (w-LED) prepared by the phosphor is (0.298, 0.311). The features of the latent fingerprint (LFP) created by NaMgLaTeO₆:Dy³⁺ can be clearly reflected on different surfaces. In summary, NaMgLaTeO₆:Dy³⁺ phosphor has proven high potential in w-LEDs production and LFP detection.