Preparation, characterisation, and europium-151 Mössbauer spectra of some carbides, nitrides, nitride-carbides, cyanides, and thiocyanates of europium

Abstract

The reaction of europium metal with HCN and (CN), at elevated temperatures has been shown to yield Eu&, EuC,, and compounds of the type EuN, C, .X-Ray parameters for these phases are reported and they are shown by 151Eu Mossbauer spectroscopy to be band systems. EuN is shown to be ionic and to contain Eu3+ ions. The reactions in liquid NH, of europium with HCN, C2H2, and NH,SCN have been shown to produce europium(l1) and europium(lii) cyanide, europium(l1i) acetylide, and europium(l1i) thiocyanate respectively. The width of the lslEu Mossbauer resonance is discussed in relation to possible bonding situations and the relationship between chemical isomer shift and bond ionicity is considered.

Structural Phase Transitions in EuC2

“…In this respect, it is important to mention that Mössbauer measurements reported on previous EuC 2 samples revealed a very broad line width (Γ = 6 mm/s), which is nearly by a factor of 2 larger than that obtained for our sample. This reflects a considerable inhomogeneity of those samples.…”

“…9 As the reported unit-cell volume of EuC 2 is much larger than those of the other RE 3þ dicarbides, it was concluded that Eu 2þ ions were present and that the carbide was wholly ionic. 151 Eu M€ ossbauer spectra corroborated these assumptions, 10 although the reported lattice parameters of the sample under investigation differed largely from those reported earlier. 8 In the most recent investigation 11 of EuC 2 , a sample was synthesized with lattice parameters quite similar to those reported in the first work on EuC 2 .…”

“…But it must be pointed out that the unit cells given for the samples under investigation ( a = 373 pm, c = 618 pm) largely deviate from the unit cells found by us (see Table ) and others ( a = 404.5 pm, c = 664.5 pm) . Therefore it can be excluded that the samples investigated in ref are pure EuC 2 .…”