Crystal structure of BaMg2Si2O7 and Eu2+ luminescence

Crystal structure of BaMg2Si2O7 was determined and refined by a combined powder X-ray and neutron Rietveld method (monoclinic, C2/c, no. 15, Z=8, a=7.24553(8) Å, b=12.71376(14) Å, c=13.74813(15) Å, β=90.2107(8)°, V=1266.44(2) Å3; Rp/Rwp=3.38%/4.77%). The structure contains a single crystallographic type of Ba atom coordinated to eight O atoms with C1 (1) site symmetry. Under 325-nm excitation Ba0.98Eu0.02Mg2Si2O7 exhibits an asymmetric emission band around 402 nm. The asymmetric shape of the emission band is likely associated with a small electron–phonon coupling in BaMg2Si2O7. The integrated intensity of the emission band was observed to remain constant over the temperature range 4.2–300 K.