Superstructure of a phosphor material Ba3MgSi2O8 determined by neutron diffraction data

Ba3MgSi2O8, a phosphor host examined for use in white-light devices and plant-growth lamps, was synthesized at 1225 °C in air. Its crystal structure has been determined and refined by a combined powder X-ray and neutron Rietveld method (View the MathML sourceP3¯, Z =3, a =9.72411(3) Å, c =7.27647(3) Å, V =595.870(5) Å3; R p/R wp=3.79%/5.03%, χ 2=4.20). Superstructure reflections, observed only in the neutron diffraction data, provided the means to establish the true unit cell and a chemically reasonable structure. The structure contains three crystallographically distinct Ba atoms—Ba1 resides in a distorted octahedral site with S 6 (View the MathML source3¯) symmetry, Ba2 in a nine-coordinate site with C3 (3) symmetry, and Ba3 in a ten-coordinate site with C1 (1) symmetry. The Mg atoms occupy distorted octahedral sites, and the Si atom occupies a distorted tetrahedral site.