High-pressure synthesis of Ruddlesden-Popper nitrides.

Layered perovskites with Ruddlesden-Popper-type structures are fundamentally important for low-dimensional properties, for example, photovoltaic hybrid iodides and superconducting copper oxides. Many such halides and oxides are known, but analogous nitrides are difficult to stabilize due to the high cation oxidation states required to balance the anion charges. Here we report the high-pressure synthesis of three single-layer Ruddlesden-Popper (KNiF type) nitrides-PrReN, NdReN and CeTaN-along with their structural characterization and properties.

A New Family of High Oxidation State Antiperovskite Nitrides: LaMN (M=Cr, Mn and Mo).

Three new nitrides LaMN (M=Cr, Mn, and Mo) have been synthesized using a high pressure azide route. These are the first examples of ternary CsCoCl-type nitrides, and show that this (MN)NLa antiperovskite structure type may be used to stabilise high oxidation-state transition metals in tetrahedral molecular [MN] nitridometallate anions. Magnetic measurements confirm that Cr and Mo are in the M state, but the M=Mn phase has an anomalously small paramagnetic moment and large cell volume.

Please Mind the Gap: Highly Condensed P-N Networks in LiP N and Li P N (NH).

Alkali nitridophosphates AP N and A P N (A=Na, K, Rb, Cs) have been known for decades. However, their Li homologues have remained elusive. In this work, the highly condensed lithium (imido)nitridophosphates LiP N and Li P N (NH) (x=1.

Defect rocksalt structures in the La-Na-N system.

Sodium azide (NaN) is a versatile nitrogen source that can be used for the synthesis of new nitrides under high-pressure and temperature conditions. Reactions between lanthanum nitride (LaN) and sodium azide (NaN) at 800°C under 8 GPa pressure have led to the discovery of two defect rocksalt phases which are the first reported ternaries in the La-Na-N system. Preliminary structure assignments have been made based on fits to powder X-ray diffraction profiles.

Low-dimensional magnetism in calcium nitridonickelate(II) CaNiN.

Calcium nitridonickelate(II) CaNiN has been prepared through a high-temperature and high-pressure azide-mediated redox reaction, demonstrating that this method can stabilise nitrides of late transition metals in relatively high oxidation states. CaNiN crystallizes in the NaHgO structure type and displays low-dimensional antiferromagnetic ordering of Ni spins.

Preparation of Bulk-Phase Nitride Perovskite LaReN and Topotactic Reduction to LaNiO -Type LaReN.

While halide and oxide perovskites are numerous and many display outstanding properties, ABN perovskite nitrides are extremely rare due to synthetic challenges arising from the low chemical potential of nitrogen and a tendency to form low-coordination nitridometallate anions. We report the preparation of a perovskite nitride LaReN through azide-mediated oxidation at high pressure. High-resolution synchrotron diffraction shows that LaReN has a low-symmetry, triclinic, perovskite superstructure resulting from orbital ordering with strong spin-orbit coupling distortions.

Preparation of iron(IV) nitridoferrate CaFeN through azide-mediated oxidation under high-pressure conditions.

Transition metal nitrides are an important class of materials with applications as abrasives, semiconductors, superconductors, Li-ion conductors, and thermoelectrics. However, high oxidation states are difficult to attain as the oxidative potential of dinitrogen is limited by its high thermodynamic stability and chemical inertness. Here we present a versatile synthesis route using azide-mediated oxidation under pressure that is used to prepare the highly oxidised ternary nitride CaFeN containing Fe ions.

Nitride Spinel: An Ultraincompressible High-Pressure Form of BeP N.

Owing to its outstanding elastic properties, the nitride spinel γ-Si N is of considered interest for materials scientists and chemists. DFT calculations suggest that Si N -analog beryllium phosphorus nitride BeP N adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite-type BeP N by single-crystal synchrotron X-ray diffraction and report the phase transition into the spinel-type phase at 47 GPa and 1800 K in a laser-heated diamond anvil cell.

The Long-Periodic Loop-Branched Chain Structure of the Oxonitridophosphate La P O N , Elucidated by a Combination of TEM and Microfocused Synchrotron Radiation.

The lanthanum oxonitridophosphate La P O N was synthesized by high-pressure metathesis from partially hydrolysed LiPN and LaCl at 750-950 °C and 7-9 GPa. The combination of transmission electron microscopy (TEM) and diffraction using microfocused synchrotron radiation revealed a monoclinic crystal structure (space group P2 /n, a=14.042(4), b=7.

Boron Phosphorus Nitride at Extremes: PN Octahedra in the High-Pressure Polymorph β-BP N.

The high-pressure behavior of non-metal nitrides is of special interest for inorganic and theoretical chemistry as well as materials science, as these compounds feature intriguing elastic properties. The double nitride α-BP N was investigated by in situ single-crystal X-ray diffraction (XRD) upon cold compression to a maximum pressure of about 42 GPa, and its isothermal bulk modulus at ambient conditions was determined to be 146(6) GPa. At maximum pressure the sample was laser-heated, which resulted in the formation of an unprecedented high-pressure polymorph, β-BP N .

Nitridophosphates: A Success Story of Nitride Synthesis.

Nitridophosphates and phosphorus nitrides are thoroughly investigated classes of nitrides. During thirty years of research, the methods for their synthesis evolved from the condensation of molecular precursors at moderate temperatures and ambient pressures to state-of-the-art high-pressure and high-temperature processes. Landmark breakthroughs made in recent years led to a comprehension-based proficiency in nitridophosphate synthesis that is illustrated by the large compositional and structural diversity of the nitridophosphates known today.

Open-Shell 3d Transition Metal Nitridophosphates M P N (M =Fe, Co, Ni) by High-Pressure Metathesis.

3d transition metal nitridophosphates M P N (M =Fe, Co, Ni) were prepared by high-pressure metathesis indicating that this route might give a systematic access to a structurally rich family of M-P-N compounds. Their structures, which are stable in air up to at least 1273 K, were determined through powder X-ray diffraction and consist of highly condensed tetra-layers of PN tetrahedra and MN octahedra. Magnetic measurements revealed paramagnetic behavior of CoP N and NiP N down to low temperatures while, FeP N exhibits an antiferromagnetic transition at T =3.

High-Pressure Metathesis of the MPON ( x ≈ 0.05) and MPO ( M = Zr, Hf) Orthophosphates.

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.

LiPrPNO: Structural Diversity of Oxonitridophosphates Accessed by High-Pressure Metathesis.

The structural diversity of tetrahedra networks of phosphates can greatly be enhanced by introduction of mixed N/O anion positions. LiPrPNO exemplifies the benefits of N/O mixed anion positions as it is the first rare-earth (oxo)nitridophosphate with a single-layered structure and a degree of condensation (atomic ratio of tetrahedra centers (P) to tetrahedra corners (N/O atoms)) of 2/5. The compound was prepared through high-pressure metathesis starting from PrF, LiPN, LiO, and PON using a hydraulic 1000t press and the multianvil technique.

Accessing Tetravalent Transition-Metal Nitridophosphates through High-Pressure Metathesis.

Advancing the attainable composition space of a compound class can lead to fascinating materials. The first tetravalent metal nitridophosphate, namely Hf P N O (x≈1.84), was prepared by high-pressure metathesis.

Puzzling Intergrowth in Cerium Nitridophosphate Unraveled by Joint Venture of Aberration-Corrected Scanning Transmission Electron Microscopy and Synchrotron Diffraction.

Thorough investigation of nitridophosphates has rapidly accelerated through development of new synthesis strategies. Here we used the recently developed high-pressure metathesis to prepare the first rare-earth metal nitridophosphate, CeLiPN, with a high degree of condensation >1/2. CeLiPN consists of an unprecedented hexagonal framework of PN tetrahedra and exhibits blue luminescence peaking at 455 nm.

High-Pressure Synthesis of Melilite-type Rare-Earth Nitridophosphates RE2P3N7 and a Ba2Cu[Si2O7]-type Polymorph.

High-pressure metathesis was proposed to be a gateway to the elusive class of rare-earth nitridophosphates. With this method the first ternary compounds of this class with sum formula RE2P3N7 were prepared, a melilite-type with RE = Pr, Nd, Sm, Eu, Ho, Yb (Ho2P3N7: P4̅21m, a = 7.3589(2), c = 4.

Rare-earth-metal nitridophosphates through high-pressure metathesis.

Developing a synthetic method to target an broad spectrum of unknown phases can lead to fascinating discoveries. The preparation of the first rare-earth-metal nitridophosphate LiNdP4 N8 is reported. High-pressure solid-state metathesis between LiPN2 and NdF3 was employed to yield a highly crystalline product.

Average and local structure, debye temperature, and structural rigidity in some oxide compounds related to phosphor hosts.

The average and local structure of the oxides Ba2SiO4, BaAl2O4, SrAl2O4, and Y2SiO5 are examined to evaluate crystal rigidity in light of recent studies suggesting that highly connected and rigid structures yield the best phosphor hosts. Simultaneous momentum-space refinements of synchrotron X-ray and neutron scattering yield accurate average crystal structures, with reliable atomic displacement parameters. The Debye temperature ΘD, which has proven to be a useful proxy for structural rigidity, is extracted from the experimental atomic displacement parameters and compared with predictions from density functional theory calculations and experimental low-temperature heat capacity measurements.