From Framework to Layers Driven by Pressure - The Monophyllo-Oxonitridophosphate β-MgSrP N O 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 β-MgSrP N O 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. β-MgSrP N O 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 Ba CuSi O . DFT calculations were performed to investigate the phase transition from α- to β-MgSrP N O and to confirm the latter as the corresponding high-pressure polymorph. Furthermore, the luminescence properties of Eu doped samples of both polymorphs were investigated and discussed, showing blue and cyan emission, respectively (α-MgSrP N O ; λ =438 nm, fwhm=46 nm/2396 cm ; β-MgSrP N O ; λ =502 nm, fwhm=42 nm/1670 cm ).