Ammonothermal Synthesis of Ba₂PO₃N – An Oxonitridophosphate with Non‐Condensed PO₃N Tetrahedra

Abstract

The ortho‐oxonitridophosphate Ba2PO3N was synthesized under ammonobasic conditions (T = 1070 K, p = 120 MPa) in custom‐built high‐temperature autoclaves, starting from red phosphorus, BaO, NaN3 and KOH. Thus, single crystals of up to several hundred µm were obtained, which were used for single‐crystal X‐ray diffraction. Ba2PO3N [Pnma (no. 62), a = 7.596(2), b = 5.796(1), c = 10.212(3) Å, Z = 4] crystallizes in the β‐K2SO4 structure type with non‐condensed [PO3N]4– ions and is isotypic to its lighter homologues EA2PO3N (EA = Ca, Sr). Powder X‐ray diffraction, energy dispersive X‐ray and Fourier Transformed Infrared spectroscopy corroborate the crystal structure. The optical band gap was determined by means of diffuse reflectance UV/Vis spectroscopy to be 4.3 eV. Eu2+ doped samples show green luminescence (λem = 534 nm, fwhm = 85 nm/2961 cm–1) when irradiated with UV light (λexc = 420 nm). However, Ba2PO3N:Eu2+ shows strong thermal quenching, even at room temperature.

Post‐Synthetic Modification: Systematic Study on a Simple Access to Nitridophosphates

“…Already initially used ambient and medium‐pressure (MP) methods ((pressure‐)ampoules, autoclaves) have enabled the preparation of various (oxo/imido)nitridophosphates, phosphorus nitrides, and related compounds [1, 3–10] . The variety of nitridophosphates, which are accessible under MP conditions, has recently been increased by hot isostatic pressing and systematic investigations using high‐temperature ammonothermal methods [2, 11–14] . Despite these advances in MP synthesis, high‐pressure high‐temperature (HP/HT) conditions are still most commonly used for nitridophosphate synthesis [1] .…”

“…[1,[3][4][5][6][7][8][9][10] The variety of nitridophosphates, which are accessible under MP conditions, has recently been increased by hot isostatic pressing and systematic investigations using high-temperature ammonothermal methods. [2,[11][12][13][14] Despite these advances in MP synthesis, highpressure high-temperature (HP/HT) conditions are still most commonly used for nitridophosphate synthesis. [1] As recently reviewed, several synthetic routes have been established within this technique, realizing a great diversity of incorpo-rated electropositive elements in anionic P/N tetrahedra substructures.…”

HIP to be Square: Simplifying Nitridophosphate Synthesis in a Hot Isostatic Press

“…To enable applications on an industrial scale, however, innovative synthetic routes are required, as sufficient sample quantities cannot be provided by established high‐pressure techniques. Therefore, an advanced ammonothermal approach using improved autoclave materials was reconsidered, enabling the access to various nitridophosphates in a medium‐pressure range and at higher temperatures . However, this method is only restrictedly applicable for industrial use due to scaling issues as it requires operations in supercritical ammonia.…”

“…Therefore, an advanced ammonothermal approach using improved autoclave materials was reconsidered, enabling the access to various nitridophosphates in a medium-pressure range and at higher temperatures. [22][23][24][25] However, this method is only restrictedly applicable for industrial use due to scaling issues as it requires operations in supercritical ammonia. Thus, the sought-after large-scale access to nitridophosphates remains a stated goal, until now.…”

HIP to be Square: Simplifying Nitridophosphate Synthesis in a Hot Isostatic Press

“…[22] Until now, P red could only be used for synthesis of nitridophosphates in combination with (supercritical) ammonia, forming intermediates like "P(NH 2 ) 5 " and "NP(NH 2 ) 2 ". [22][23][24]32] Applying the HIP approach the use of ammonia can be circumvented. Here, P red initially transforms most likely into gaseous/molecular and highly reactive phosphorus P 4 (or P 2 ) under the given conditions [Eq.…”