Experimental and first-principles studies on photoluminescence of Ce3+-doped calcium chloroborate Ca2BO3Cl

Abstract

The luminescense properties of Ce3+ ions in Ca2BO3Cl were studied upon excitation in the 3–20 eV range. It is shown that because of the presence of different charge compensating defects, the various types of centers involving Ce3+ are formed in Ca2BO3Cl. Based on the results obtained, the values of the crystal field splitting and the centroid shift of the Ce3+ 5d configuration for locally uncompensated Ce3+ centers were determined and compared with those of Ce3+ ions in some other inorganic compounds. The DFT calculations were utilized to study the band structure of Ca2BO3Cl, the 4f→5d transitions of Ce3+ ions and the intrinsic defects of this compound. The calculated band gap of Ca2BO3Cl (7.22 eV) is consistent with the experimental value of 7.35 eV, and the 4f→5d transition energies for Ce3+ ions on the two sevenfold coordination sites confirm spectral assignments based on the luminescent measurements. The experimental results and first-principles calculations show that the introduction of Na+ hardly influences the luminescence properties of Ce3+-doped Ca2BO3Cl. The possible processes occurring in Ca2BO3Cl:Eu2+, Ce3+ persistent phosphors are also discussed based on the combined theoretical and experimental results.