Effects of changing the M2+ cation on the crystal structure and optical properties of divalent samarium-doped MAl2Si2O8 (M = Ca, Sr, Ba)

Abstract

In order to investigate the effects of changing the cation on crystal structure and optical properties of divalent samarium-doped MAl₂Si₂O₈, the Sm²⁺ doped triclinic CaAl₂Si₂O₈ (CASO), monoclinic SrAl₂Si₂O₈ (SASO) and BaAl₂Si₂O₈ (M-BASO) as well as hexagonal BaAl₂Si₂O₈ (H-BASO) compounds have been synthesized using a polymerizable-complex technique under a reducing atmosphere. At room temperature, under N-UV or blue excitation, Sm²⁺ doped SASO, M-BASO and H-BASO showed strong red emission, which widens the group of novel red-emitting materials. The emission bands of Sm²⁺ consist of a broad 4f–5d transition band and sharp f–f transition lines. The correlation between the crystal structure and the 4f–4f transition emission intensity of Sm²⁺ as well as the excitation peaks of the 5d energy level is discussed in detail, and the theoretical analysis is in good agreement with our experimental results. These are essential to understand the relationship between the crystal structure and luminescence properties, which are fundamental to design luminescent materials of Sm systems.