From Framework to Layers Driven by Pressure - The Monophyllo-Oxonitridophosphate ß-MgSrP3 N5 O2 and Comparison to its α-Polymorph.

Oxonitridophosphates exhibit the potential for broad structural diversity, making them promising host-compounds in phosphor-converted light-emitting diode applications. The novel monophyllo-oxonitridophosphate ß-MgSrP3 N5 O2 was obtained by using the high-pressure multianvil technique. The crystal structure was solved and refined based on single-crystal X-ray diffraction data and confirmed by powder X-ray diffraction. ß-MgSrP3 N5 O2 crystallizes in the orthorhombic space group Cmme (no. 67, a=8.8109(6), b=12.8096(6), c=4.9065(3) Å, Z=4) and has a structure related to that of Ba2 CuSi2 O7 . DFT calculations were performed to investigate the phase transition from α- to ß-MgSrP3 N5 O2 and to confirm the latter as the corresponding high-pressure polymorph. Furthermore, the luminescence properties of Eu2+ doped samples of both polymorphs were investigated and discussed, showing blue and cyan emission, respectively (α-MgSrP3 N5 O2 ; λmax =438 nm, fwhm=46 nm/2396 cm-1 ; ß-MgSrP3 N5 O2 ; λmax =502 nm, fwhm=42 nm/1670 cm-1 ).