Synthesis, characterisation and properties of rare earth oxyselenides A₄O₄Se₃(A = Eu, Gd, Tb, Dy, Ho, Er, Yb and Y)

Abstract

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Quaternary Selenides EuLnCuSe3: Synthesis, Structures, Properties and In Silico Studies

“…Its experimental IR spectrum is, in general, the result of overlapping of closely positioned bands without any large gaps between the IR active vibrations (Figure 8). It should also be noted that all the reported selenides, except for the La-based one, are contaminated by the Ln 4 O 4 Se 3 [74] or Ln 2 SeO 2 [75] impurities (see discussion above). Thus, additional bands from the Ln-Se vibrations of the oxyselenides are also expected in the same range as for the quaternary selenides.…”

“…Most of the unmodified Kubelka-Munk spectra exhibit a shoulder at longer wavelengths preceding the onset of an evident fundamental absorption. This shoulder is associated with oxyselenide impurities (Table 1) that are known to be semiconductors with the band gap of 1.02-1.46 eV [74]. Thus, to estimate the band gap value of the discussed selenides, an additional correction was applied with respect to impurities [78].…”

The magnetic and electronic properties of oxyselenides—influence of transition metal ions and lanthanides

“…These sheets are separated by layers containing both Se 2− and diselenide Se 2 2− anions (Strobel et al, 2008;Tuxworth et al, 2015). Whilst the [Ln 4 O 4 ] 4+ sheets change little with Ln, the arrangement of Se 2− and Se 2 2− anions in the interlayers varies with Ln 3+ ionic radii (Tuxworth et al, 2015). Longrange antiferromagnetic order occurs for Ln = Gd, Tb and Dy phases but has not been observed down to 1.8 K for other analogues.…”

“…Similar challenges are faced when preparing single crystals of oxyselenides. Most oxyselenide single crystals have been grown from a flux, usually KCl, (Ijjaali et al, 2003)or a eutectic mix of NaI/KI, (Nitsche et al, 2014;Peschke et al, 2015) but CsI (Tuxworth et al, 2015) I 2 (Meerschaut et al, 1998(Meerschaut et al, , 2001a and Na 2 Se x (Park et al, 1993) fluxes have also been used.…”

“…The Ln 4 O 4 Se 3 (Ln = La -Nd, Eu -Er, Yb and Y) family adopts crystal structures composed of fluorite-like [Ln 4 O 4 ] 4+ oxide sheets built from edge-linked Ln 4 O tetrahedra. These sheets are separated by layers containing both Se 2− and diselenide Se 2 2− anions (Strobel et al, 2008;Tuxworth et al, 2015). Whilst the [Ln 4 O 4 ] 4+ sheets change little with Ln, the arrangement of Se 2− and Se 2 2− anions in the interlayers varies with Ln 3+ ionic radii (Tuxworth et al, 2015).…”