Study on structural, morphological, and spectral properties of LiMPO4:Eu3+, B3+ (M = Zn, Sr) phosphors and latent fingerprint applications

Boron influences the melting point, crystallization, and both the optical and structural characteristics of ceramic materials. The effect of boron on the structural, morphological, and spectral properties for LiMPO₄:xEu³⁺, yB³⁺ (where M = Zn or Sr and x = 3 mol%, y = 0–100 mol%) phosphors was investigated using materials fabricated with the solid-state method. In XRD results, LiZnPO₄:Eu³⁺, B³⁺ series showed a single-phase structure up to 100 mol%, while LiSrPO₄:Eu³⁺, B³⁺ samples exhibited a low monoclinic phase at low concentrations. In SEM micrographs, the flux effect of boron caused growth in LiMPO₄:Eu³⁺, B³⁺ (M = Zn, Sr) grains sizes. As the B³⁺ concentration increases, PL emissions for both phosphor series increased up to 100 mol%, and the luminescence intensities increased over 8 times. Judd-Ofelt (JO) parameters (Ω₂, Ω₄) showed a slightly increasing trend for LiZnPO₄:Eu³⁺, B³⁺, whilst the change in Ω₂ and Ω₄ parameters was limited for LiSrPO₄:Eu³⁺, B³⁺ series. As the B³⁺ concentration increased, the observed lifetime (τ) of LiZnPO₄:Eu³⁺, B³⁺ with a bi-exponential decay decreased, whereas the τ lifetime for LiSrPO₄:Eu³⁺, B³⁺ with a mono exponential decay increased. The quantum efficiencies for LiSrPO₄:Eu³⁺, B³⁺ phosphors varied between 89.83 %–96.78 % and exhibited approximately twice the efficiency of LiZnPO₄:Eu³⁺, B³⁺. The usability of optimized LiMPO₄:xEu³⁺, yB³⁺ (where M = Zn, Sr and x = 3 mol%, y = 100 mol%) phosphors was investigated for latent fingerprint applications.