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Kloss, Simon D.; Weidmann, Niels; Schnick, Wolfgang (2017): Antiperovskite Nitridophosphate Oxide Ho-3[ PN4] O by High-Pressure Metathesis. In: European Journal of inorganic Chemistry, Nr. 13: S. 1930-1937
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Rare-earth nitridophosphates are a recently discovered class of materials, which are accessible by high- pressure metathesis. Antiperovskite-type Ho-3[ PN4] O was synthesized from HoF3, LiPN2, Li-3 N, and Li2O at 5 GPa and ca. 1025 degrees C by this method and the multianvil technique. Ho3[ PN4] O contains rarely observed isolated PN4 tetrahedra and can be derived by the hierarchical substitution of the ABX(3) perovskite, in which Ho occupies the X positions, O occupies the B position, and the PN4 tetrahedra occupy the A position. The structure was refined on the basis of powder diffraction data [ I4/ mcm, a = 6.36112( 3), c = 10.5571( 1) angstrom, Z = 4, R-wp = 0.04, R-Bragg = 0.01, x(2) = 2.275] starting from the structural model of isotypic Gd-3[ SiN3O] O. To characterize Ho3[ PN4] O, elemental analyses were performed through energy- dispersive X- ray spectroscopy ( EDX) and inductively coupled plasma optical emission spectroscopy ( ICP- OES). Ho3[ PN4] O is paramagnetic down to low temperatures with mu eff = 10.43( 1) mu(B) and a Curie temperature ( Theta) of 0.11( 4) K. It shows the optical characteristics of Ho3+ ions and vibrations corresponding to isolated PN4 tetrahedra. On the basis of DFT calculations [ generalized gradient approximation ( GGA)], Ho3[ PN4] O has an indirect band gap of 1.87 eV. We demonstrate the versatility of high- pressure metathesis by attaining the low end of the P/ N atomic ratio. = 1/ 4. This confirms the previous assumption that rare- earth nitridophosphates with. = 1/ 2 to 1/ 4 are feasible by this method.