Synthesis and characterisation of the ternary nitride, Sr₂TaN₃

The ternary nitridotantalate, Sr₂TaN₃ has been synthesised via the solid state reaction of strontium subnitride, Sr₂N, with either of the tantalum nitrides TaN or Ta₃N₅ in a sealed system under argon at elevated temperatures. The structure of Sr₂TaN₃ was determined for the first time by Rietveld refinement against powder X-ray diffraction data. The compound crystallises with the Ba₂ZnO₃ structure [monoclinic space group C2/c (No.15), a = 5.9835(1) Å, b = 11.2832(2) Å, c = 12.5814(2) Å, β = 92.26(1)°, V = 848.75(2) ų, Z = 8] and is isostructural with other A^II₂M^VN₃ nitrides, Ba₂TaN₃, Sr(Ba)₂NbN₃ and Sr₂VN₃. The nitride contains infinite chains of corner-sharing TaN₄ tetrahedral anions, ¹_∞[TaN₂N_2/2]^4-, with Ta-N distances of 1.83-1.97 Å. Magnetic measurements are consistent with a nitridotantalate(V).