Structural consideration on the emission properties of Eu2+-doped Li2BaMgP2O8 and Na2BaMgP2O8 orthophosphates

Li2BaMgP2O8 and Na2BaMgP2O8 were synthesized by a standard solid state reaction. Structural analyses have revealed that Li2BaMgP2O8 is a member of the olgite family, as is the case with Na2BaMgP2O8. The layer-framework build up by corner-sharing MgO6 octahedra and PO4 tetrahedra twists around C3 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 Li2BaMgP2O8 and Na2BaMgP2O8 exhibited intense violet–blue emission under ultraviolet excitation. They were characterized by two emission centers; Eu2+ ions replacing A-site cations (Ba2+) and B-site cations (Li+ or Na+). The B-site Eu2+ emission was very sensitive to the twisting behavior caused by original B-site cation.