Ammonothermal Synthesis of Luminescent Imidonitridophosphate Ba₄P₄N₈(NH)₂:Eu²⁺

Abstract

The structural variability of a compound class is an important criterion for the research into phosphor host lattices for phosphor‐converted light‐emitting diodes (pc‐LEDs). Especially, nitridophosphates and the related class of imidonitridophosphates are promising candidates. Recently, the ammonothermal approach has opened a systematic access to this substance class with larger sample quantities. We present the successful ammonothermal synthesis of the imidonitridophosphate Ba4P4N8(NH)2:Eu2+. Its crystal structure is solved by X‐ray diffraction and it crystallizes in space group Cc (no. 9) with lattice parameters a = 12.5250(3), b = 12.5566(4), c = 7.3882(2) Å and β = 102.9793(10)°. For the first time, adamantane‐type (imido)nitridophosphate anions [P4N8(NH)2]8− are observed next to metal ions other than alkali metals in a compound. The presence of imide groups in the structure and the identification of preferred positions for the hydrogen atoms are performed using a combination of quantum chemical calculations, Fourier‐transform infrared, and solid‐state NMR spectroscopy. Eu2+ doped samples exhibit cyan emission (λmax = 498 nm, fwhm = 50 nm/1981 cm−1) when excited with ultraviolet light with an impressive internal quantum efficiency (IQE) of 41 %, which represents the first benchmark for imidonitridophosphates and is promising for potential industrial application of this compound class.