Sr3 P3 N7 : Complementary Approach by Ammonothermal and High-Pressure Syntheses

Abstract

Nitridophosphates exhibit an intriguing structural diversity with different structural motifs, for example, chains, layers or frameworks. In this contribution the novel nitridophosphate Sr₃ P₃ N₇ with unprecedented dreier double chains is presented. Crystalline powders were synthesized using the ammonothermal method, while single crystals were obtained by a high-pressure multianvil technique. The crystal structure of Sr₃ P₃ N₇ was solved and refined from single-crystal X-ray diffraction and confirmed by powder X-ray methods. Sr₃ P₃ N₇ 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. The optical band gap was estimated to be 4.4 eV using diffuse reflectance UV/Vis spectroscopy. Upon doping with Eu²⁺ , Sr₃ P₃ N₇ shows a broad deep-red to infrared emission (λ_em =681 nm, fwhm≈3402 cm^-1 ) with an internal quantum efficiency of 42 %.

Keywords: ammonothermal synthesis; crystal growth; high-pressure chemistry; luminescence; nitridophosphates.