High-Pressure Metathesis of the M_1–xPO_3+4xN_1–4x (x ≈ 0.05) and M_0.75PO₄ (M = Zr, Hf) Orthophosphates

Abstract

We describe the oxonitridophosphates MPON ( x ≈ 0.05) and the isotypic oxophosphates MPO ( M = Zr, Hf) obtained by high-pressure metathesis. The structures (ZrSiO-type, space group I4/ amd (no. 141), a = 6.5335(7)-6.6178(12), c = 5.7699(7)-5.8409(9) Å, Z = 4) were refined from single-crystal X-ray diffraction data, and the powder samples were examined with quantitative Rietveld refinement. Infrared spectroscopy did not indicate the presence of X-H ( X = O, N) bonds. The optical band gaps, between 3.5 and 4.3 eV, were estimated from UV-vis data using the Kubelka-Munk function under assumption of a direct band gap. Temperature-dependent powder X-ray diffraction showed a phase transformation of the MPO ( M = Zr, Hf) compounds to ambient pressure polymorphs at 780 (Zr) and 900 °C (Hf). The preparation of the nitrogen containing compounds exemplifies the systematic access to the new class of group 4 nitridophosphates granted by high-pressure metathesis. Moreover, we show that high-pressure metathesis can also be used for the preparation of metastable oxophosphates.

The Long‐Periodic Loop‐Branched Chain Structure of the Oxonitridophosphate La21P40O46N57, Elucidated by a Combination of TEM and Microfocused Synchrotron Radiation

“…With mixed O/N atom positions in oxonitridophosphates, the structural diversity may be further increased, and the few known examples feature an intriguing structural chemistry with unique building blocks. LiPr 2 P 4 N 7 O 3 , for example, is the first nitridophosphate with single layers of tetrahedra, while CaMg 2 P 6 O 3 N 10 and Hf 9− x P 24 N 52−4 x O 4 x ( x ≈1.84) crystallize in the Ti 5 B 12 O 26 type with interpenetrating adamantanoid (diamond‐like) tetrahedra frameworks. Although multinary systems like oxonitridophosphates, in principle, offer a greater variety with respect to composition and structure, but are often underdeveloped when compared to the parent classes of compounds, for example, oxophosphates and nitridophosphates.…”

High‐Pressure Synthesis of Sc5P12N23O3 and Ti5P12N24O2 by Activation of the Binary Nitrides ScN and TiN with NH4F

“…The first systematic approach to a variety of TM compounds is represented by metathesis reactions under high-pressure hightemperature conditions as shown for MP 8 N 14 (M = Fe, Co, Ni), M 1À x PO 3 + 4x N 1À 4x (x � 0.05), M 0.75 PO 4 (M = Zr, Hf) and Hf 9À x P 24 N 52À 4x O 4x (x � 1.84). [12][13][14][15] High-pressure metathesis with the formation of lithium halides from LiPN 2 and TM halides, however, features inherent drawbacks. Like many HP/HT syntheses, this approach typically yields microcrystalline powders which impede precise structure elucidation by conventional single-crystal X-ray diffraction.…”

“…The first systematic approach to a variety of TM compounds is represented by metathesis reactions under high‐pressure high‐temperature conditions as shown for M P 8 N 14 ( M =Fe, Co, Ni), M 1− x PO 3+4 x N 1−4 x ( x ≈0.05), M 0.75 PO 4 ( M =Zr, Hf) and Hf 9− x P 24 N 52−4 x O 4 x ( x ≈1.84). [ 12 , 13 , 14 , 15 ]…”