Sr₃P₃N₇: Complementary Approach by Ammonothermal and High‐Pressure Syntheses

Abstract

Nitridophosphates exhibit an intriguing structural diversity with different structuralm otifs, for example, chains, layers or frameworks. In this contribution the novel nitridophosphate Sr 3 P 3 N 7 with unprecedented dreier double chains is presented. Crystalline powders were synthesized using the ammonothermal method, while single crystals wereo btained by ah igh-pressurem ultianvil technique. The crystal structure of Sr 3 P 3 N 7 was solved and refinedf rom single-crystal X-ray diffraction and confirmed by powderX -ray meth-ods. Sr 3 P 3 N 7 crystallizes in monoclinic space group P2/c. Energy-dispersive X-ray and Fourier-transformed infrared spectroscopy were conducted to confirm the chemical composition, as well as the absence of NH x functionality. Theo ptical band gap was estimated to be 4.4 eV using diffuse re-flectanceU V/Vis spectroscopy.U pon doping with Eu 2 + , Sr 3 P 3 N 7 showsabroad deep-red to infrared emission (l em = 681 nm, fwhm % 3402 cm À1 )w ith an internal quantum efficiencyo f42%.

Nitridophosphate‐Based Ultra‐Narrow‐Band Blue‐Emitters: Luminescence Properties of AEP8N14:Eu2+ (AE=Ca, Sr, Ba)

“…The corresponding crystal structures are built up from anionic PN 4 tetrahedra networks that host the cations . Among ternary all‐nitride representatives, only AE P 2 N 4 :Eu 2+ ( AE =Ca, Sr, Ba) and Sr 3 P 3 N 7 :Eu 2+ are known . However, these few members illustrate the versatility of nitridophosphates, as they cover a major part of the visible spectrum ( λ emi =450–680 nm) and also feature high quantum efficiencies even for non‐optimized powder samples .…”

“…Among ternary all‐nitride representatives, only AE P 2 N 4 :Eu 2+ ( AE =Ca, Sr, Ba) and Sr 3 P 3 N 7 :Eu 2+ are known . However, these few members illustrate the versatility of nitridophosphates, as they cover a major part of the visible spectrum ( λ emi =450–680 nm) and also feature high quantum efficiencies even for non‐optimized powder samples . The great potential of nitridophosphates is underlined by zeolite‐like compounds Ba 3 P 5 N 10 X :Eu 2+ ( X =Cl, Br, I), of which Ba 3 P 5 N 10 Br:Eu 2+ has to be highlighted, as it has been discussed as a natural‐white‐light single emitter …”

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] .…”

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

“…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.…”

“…[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.…”