Structural consideration on the emission properties of Eu ²-doped Li ₂BaMgP ₂O ₈ and Na ₂BaMgP ₂O ₈ orthophosphates

Li ₂BaMgP ₂O ₈ and Na ₂BaMgP ₂O ₈ were synthesized by a standard solid state reaction. Structural analyses have revealed that Li ₂BaMgP ₂O ₈ is a member of the olgite family, as is the case with Na ₂BaMgP ₂O ₈. The layer-framework build up by corner-sharing MgO ₆ octahedra and PO ₄ tetrahedra twists around C ₃ axes to match the size of B-site cation (Li ⁺ or Na ⁺). This twisting affects the coordination number for the B-site cation and unit cell size. Eu-doped Li ₂BaMgP ₂O ₈ and Na ₂BaMgP ₂O ₈ exhibited intense violet-blue emission under ultraviolet excitation. They were characterized by two emission centers; Eu ² ions replacing A-site cations (Ba ²) and B-site cations (Li ⁺ or Na ⁺). The B-site Eu ² emission was very sensitive to the twisting behavior caused by original B-site cation.