Structure–composition relationships and optical properties in cerium-substituted (Sr,Ba)3(Y,La)(BO3)3 borate phosphors

Abstract

Relationships between the structure and composition, and their influence on the optical properties, of a family of cerium-substituted borate compounds with formula A₃RE(BO₃)₃ (A = Ba, Sr; RE = Y, La) are studied using a combination of high resolution synchrotron X-ray powder diffraction and photoluminescence. Examination of the coordination environment of the Ce³⁺ active site polyhedra coupled with photoluminescence at 77 K reveal three distinct excitation bands corresponding to Ce³⁺ located on three distinct crystallographic sites. Comparing the position of these excitation bands with crystal field splitting effects due to changes in polyhedral volumes and distortions suggest an assignment of the three excitation bands. These compounds are efficiently excited by UV light (≈340 nm) with blue emission at a maximum wavelength of 413 nm for Ba₃Y(BO₃)₃:Ce³⁺,Na⁺, 422 nm for Sr₃Y(BO₃)₃:Ce³⁺,Na⁺, and 440 nm for Sr₃La(BO₃)₃:Ce³⁺,Na⁺. The most efficient compound was determined to be Sr₃La(BO₃)₃:Ce³⁺,Na⁺ with a quantum yield of 50%.