From Framework to Layers Driven by Pressure - the Monophyllo-Oxonitridophosphate -Mgsrp3n5o2 and Comparison to Its -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 beta-MgSrP3N5O2 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. beta-MgSrP3N5O2 crystallizes in the orthorhombic space group Cmme (no. 67, a=8.8109(6), b=12.8096(6), c=4.9065(3) angstrom, Z=4) and has a structure related to that of Ba2CuSi2O7. DFT calculations were performed to investigate the phase transition from alpha- to beta-MgSrP3N5O2 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 (alpha-MgSrP3N5O2; lambda(max)=438 nm, fwhm=46 nm/2396 cm(-1); beta-MgSrP3N5O2; lambda(max)=502 nm, fwhm=42 nm/1670 cm(-1)).