A pure blue Ca2--Mg SiO3Cl2: yEu2+ phosphor synthesized by in-situ self-reduction process in air based on oxygen vacancies

A pure blue Ca2-x-yMgxSiO3Cl2: yEu2+ phosphor was successfully synthesized by high-temperature solid-state method in air. The as prepared phosphors emitted a pure 446 nm blue light excited by 346 nm, which typically corresponded to 4f6-5d1 transitions of Eu2+. The Ca1.58M0.4SiO3Cl2: 0.02 Eu2+ was the optimum composition, and the concentration quenching of Eu2+ was determined to be a dipole-dipole interaction mechanism. However, Ca1.58M0.4SiO3Cl2: 0.02 Eui+ (M = Ca, Sr, Ba), being prepared parallel in the same process, didn't exhibit obvious blue emissions. Theoretically, since the smaller Mg2+ could easily occupy the sites of bigger Ca2+ in the Ca2SiO3Cl2 matrix, leading to a lattice distortion, so that the dipole moment was formed by distortions of SiO4 tetrahedra, which make Ca2-x-yMgxSiO3Cl2 become stable with an unusual structure of PDF #42–1455 (Ca2SiO3Cl2), and thus create a circumstance for forming oxygen vacancies surrounding the SiO4 units, as a result the residual electrons were released, so that Eu3+ ions could be easily shifted to Eu2+ in-situ. Furthermore, the fluorescence lifetime of the Ca1.58Mg0.4SiO3Cl2: 0.02 Eu2+ phosphor was determined to be 504.9 ns, the quantum efficiency was 41.36%, and the CIE chromaticity coordinates was (0.1504, 0.0344). It suggested that the as prepared phosphor possessed its talent application in the field of lighting and display as a pure blue component.