Insight into the structural and optical properties of novel Eu activated NaCl ceramic prepared by cold sintering method

The NaCl:xEu 3+ (x = 0.002, 0.004, 0.006, 0.008, 0.01, 0.02) ceramics were synthesized using a cold sintering method under varying temperature and pressure conditions. The impact of Eu 3+ ions on the structural and optical properties of NaCl ceramics was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), analytical scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), UV–visible spectroscopy, reflectance spectroscopy, photoluminescence (PL) spectroscopy, and fluorescence lifetime measurements. XRD analyses confirmed the incorporation of Eu ions into the matrix lattice. SEM results indicated that the ceramics achieved high density when the uniaxial pressure exceeded 300 MPa. EDS analysis demonstrated a well-distributed presence of rare earth ions, devoid of impurities. PL spectroscopy revealed that the intensity of the emission spectra increased the increase of Eu 3+ concentration and observed the optimal luminescence performance at x = 0.01 mol% and a sintering temperature of 125 °C. XPS results indicated that the Eu ions were predominantly in a trivalent state within the NaCl ceramics. Collectively, the above results provide valuable insights for the preparation of rare-earth doped alkali halide ceramics using cold sintering technology.