Optical and mechanical properties of NaCl: Ce³⁺ crystal grown by the Czochralski method

The pure and Ce³⁺-doped NaCl crystals were grown using the resistance heating Czochralski method. The structural, mechanical, and optical properties of the grown crystal were investigated by X-ray diffraction (XRD), micro-hardness, optical absorption, photoluminescence (PL), PL excitation (PLE) spectroscopy, and decay time measurement. The XRD data indicated that the NaCl host lattice was compressed when Ce atoms were incorporated and the peaks shifted to the large angle side. The ICP-AES and XPS analyses verified that Ce³⁺ is the dominant state of cerium in NaCl crystal. The hardness of the NaCl:Ce³⁺ crystal was larger than that of pure NaCl crystal and it was anisotropic. Optical absorption confirmed that the three states of 5d level splitting of Ce correspond to the absorption peaks of 202, 215, and 227 nm. The intense emissions located at 342 and 356 nm were attributed to the radiation transitions 5d → ²F_5/2 and 5d → ²F_7/2 in Ce³⁺, respectively. The energy-level scheme for the Ce³⁺ ion in the NaCl crystal was proposed from the PL and PLE analysis. The luminescence decay time of NaCl:Ce³⁺ crystal is 38.57 ± 0.16 ns. These observations indicate that the NaCl:Ce³⁺ crystal should be a promising material for use in radiation dosimetry and scintillation applications.