Interplay between Crystal Structure and Photoluminescence Properties of β-Ca3SiO4Cl2:Eu2+

The crystal structure of β-Ca3SiO4Cl2 was determined by the ab initio structure determination method based on the synchrotron powder XRD data for the first time, and the luminescence properties of a Eu2+-doped β-Ca3SiO4Cl2 phosphor were characterized. β-Ca3SiO4Cl2 was found to be monoclinic (space group P21/c) with the lattice parameters, a = 5.91234(1) A, b = 10.20128(1) A, c = 10.98866(1) A, β = 90.3423(1)°. This structure can be considered as an intergrowth structure built up from alternating stacks of two layered sublattices, ∞2[Ca2SiO4] and ∞2[CaCl2], along the [100] direction. In this structure, the Ca atoms occupy three crystallographically distinct sites: Ca1O4Cl3, Ca2O5Cl2, and Ca3O3Cl4. The photoluminescence of the Eu2+-doped Ca3SiO4Cl2 phosphor excited at 450 nm blue light shows the 150 nm wide-band emission peaked at 635 nm with about 70% quantum efficiency. The photoluminescence properties, such as centroid shifts, crystal-field splitting, and Stokes shifts, were correlated with the crystal s...