Crystal structure of the monoclinic Ba_2MgSi_2O_7 persistent luminescence material

摘要

Previously unknown structure of Ba_2MgSi_2O_7 persistent luminescence material was observed to be monoclinic with the space group C2/c (No. 15), Z = 4, a = 8.41275(1), b = 10.71005(1), c = 8.43871(1) A and β= 110.71(1)° based on X-ray powder diffraction data. The structure is composed of discrete [Si_2O_7]~(6-) units connected by tetrahedrally coordinated Mg atoms to form sheets in the ac plane. Layers of eight-coordinated Ba atoms run parallel to the Mg(Si_2O_7) sheets perpendicular to the unit cell b axis.