Comparative Analysis of Sm3+-doped BaWO4 and CaWO4 Phosphors: Properties and Application in Latent Fingerprints and Anti-Counterfeiting

Self-activated tungstates doped with lanthanide ions are an excellent class of phosphor materials, exhibiting promising luminescence efficiency as well as stability which opens up their vast arena of applications. In this work, a detailed comparative study has been carried out on Sm³⁺ doped Ba/CaWO₄ phosphors, synthesized via solid state reaction route. The structural, morphological and photo-physical properties have been investigated through various analytical techniques. The optical band gap and the refractive index of the phosphors have been estimated through diffuse reflectance spectroscopy. A 5-fold enhancement of the emission intensity is observed in CaWO₄ as compared to BaWO₄ phosphors owing to high asymmetrical environment. The underlying mechanisms of photoluminescence and energy transfer process (WO₄²⁺→Sm³⁺) are discussed in detail. The colour tuning from orange red to pure red emission is obtained from the Commission International de l'Eclairage (CIE) diagram. Better luminescent properties with desirable quantum yield, absorption efficiency and suitable Correlated Colour Temperature (CCT) and colour purity (91%) values allow the optimised phosphors for diverse potential applications such as solid-state lighting, security ink for anti-counterfeiting, latent fingerprint detection, etc.