Novel red-emitting Cd2MgTeO6:Eu3+ phosphors with an abnormal thermal quenching for application in w-LEDs and potential fingerprint detection

Abstract

A new series of red luminescent Cd2MgTeO6:xEu3+ (x = 0.5–50 mol%) phosphors was successfully synthesized through a high-temperature solid-phase reaction at 1000 °C. The synthesized phosphors were investigated for their phase purity, surface morphology, elemental distribution, and luminescence properties. Strong orange-red light emission (617 nm) was observed upon excitation at 398 nm, which was attributed to the electric dipole 5D0-7F2 transition of Eu3+. The optimal doping concentration was found to be x = 20 mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of all the Cd2MgTeO6:Eu3+ samples were found to be located in the red region and were almost the same. The Cd2MgTeO6: 20 mol%Eu3+ phosphors exhibited an unusual thermal quenching behavior, maintaining 102% of the initial intensity, thus possessing excellent thermostability. Moreover, the manufactured white light diode demonstrated a good color rendering index (Ra = 89) with the coordinates of (0.344, 0.330) by the Commission International de L'Eclairage (CIE). Additionally, the Cd2MgTeO6: 20 mol%Eu3+ phosphor was surface-functionalized with oleic acid (OA) (Cd2MgTeO6: 20 mol%Eu3+@OA) to aid in the identification of Level I-III fingerprint details with high resolution and contrast. Good visualization of the latent fingerprint (LFP) was observed on different substrates. Therefore, Cd2MgTeO6:Eu3+ phosphors hold great promise for the visualization of w-LEDs and LFPs.