The Crystal Structures of Er₃OFS₃ and Er₃OF₃S₂: Two Erbium Oxide Fluoride Sulfides with Condensed Tetrahedral [ZEr₄] Units (Z = O and F) 

Abstract

Abstract. The two new compounds Er3OFS3 and Er3OF3S2 vary mostly in their fluoride and sulfide content. The fluoride-poor erbium(III) oxide fluoride sulfide Er3OFS3 crystallizes in the tetragonal space group I4/mmm (a = 374.86(2), c = 2068.41(9) pm, Z = 2) with two crystallographically different Er 3+ cations. (Er1) 3+ is surrounded by six S 2-anions in the shape of a slightly distorted octahedron, whereas (Er2) 3+ exhibits a coordination number of eight (4 × O 2-/F -and 4 × S 2-arranged as a square antiprism). In the crystal structure of Er3OFS3 edge-sharing tetrahedral [ZEr4] 10.5+ units (Z n-= 50% O 2-+ 50% F -) form condensed 2 ∞ [OFEr2] 3+ layers. These layers alternate with 2 ∞ [ErS3] 3-sheets, built up of [ErS6] 9-octahedra, which are connected via four common edges, to complete the three-dimensional crystal structure of Er3OFS3. The fluoride-rich erbium(III) oxide fluoride sulfide Er3OF3S2 crystallizes in the orthorhombic space group Ccce (a = 538.31(2), b = 1892.03(9), c = 538.27(2) pm, Z = 4). Two crystallographically distinct Er 3+ cations are present in its crystal structure. (Er1) 3+ is surrounded by eight Z n-anions (Z = 25% O 2-+ 75% F -) in the shape of a twisted square antiprism, while (Er2) 3+ holds a coordination number of nine (4 × O 2-/F -and 5 × S 2-arranged as a monocapped square antiprism), copying the coordination geometry of the Er 3+ cations in PbFCl-type ErFS. The threedimensional structure of Er3OF3S2 is built up of S 2-sheets and 2 ∞ [OF3Er3] 4+ double layers, which are formed by strongly contorted tetrahedral [ZEr4] 10.75+ units (Z n-= 25% O 2-+ 75% F -). The crystals of this compound show a prominent superstructure in the tetragonal space group I4/mmm with a = 380.59(3), c = 1892.03(9) pm and Z = 2. In the crystal structures of both title compounds, the light anions O 2-and F -occupy one crystallographically unique Wyckoff position in a statistic allocation. Subject to the O/F content in the formulae, the ratio of O 2-: F -is 1 : 1 in Er3OFS3 and 1 : 3 in Er3OF3S2.

Zwei strukturverwandte Oxidnitridchalkogenide der Lanthanoide: Tb3ONSe2 und La5O2NS4

“…Um in den Kristallstrukturen von Tb 3 ONSe 2 und La 5 O 2 NS 4 die anhand von Röntgenbeugungsdaten getroffenen Zuordnungen der Leichtanionen O 2– und N 3– auf bestimmte kristallographische Lagen zu bestätigen, wurden mit Hilfe des Bond‐Valence‐Konzeptes [25–27] über interatomare Abstände die Ladungen der kristallographisch unterscheidbaren Leichtanionen berechnet und mit jenen, die aus den Kristallstrukturverfeinerungen hervorgegangen sind, verglichen. Anders als für O 2– und F – bei den Oxidfluoridsulfiden Er 3 OFS 3 und Er 3 OF 3 S 2 28 zeigte es sich jedoch, dass eine Unterscheidung der O 2– ‐ und N 3– ‐Anionen auf der Basis dieses Konzeptes hier nicht möglich ist. Je nach Wahl der Startwerte r 0 ergibt sich für die entsprechenden Leichtanionen eine Ladung von rund –2 oder nur wenig höher, im Detail r 0 (Tb 3+ –O 2– ) = –2.03 und r 0 (La 3+ –O 2– ) = –2.17 26 sowie r 0 (Tb 3+ –N 3– ) = –2.20 und r 0 (La 3+ –N 3– ) = –2.34 (mit b = 0.37 27).…”

Luminescence and Spectroscopic Studies of (Y0.99Ce0.01)3OF3S2: A New Orange Yellow‐emitting Oxyfluorosulfide Phosphor for LEDs

“…Therefore, this class of material is expected to combine the unique features of fluorides with lower phonon energy and sulfides with strong covalency; therefore, an efficient and longer wavelength emission from Ce 3+ is expected. To the best of our knowledge, the luminescence property of oxyfluorosulfide-based phosphor, 8,9 into which oxygen will be incorporated, has yet to be investigated. Pure phase of (Y 1-x Ce x ) 3 OF 3 S 2 can be obtained when prepared at temperature of 850-1000°C.…”

Two Hexagonal Series of Lanthanoid(III) Oxide Fluoride Selenides: M6O2F8Se3 (M = La – Nd) and M2OF2Se (M = Nd, Sm, Gd – Ho)

“…Major reason for this finding might be the fact that O 2– and F – anions exhibit similar ionic radii making mixed occupancies possible to occur. This behavior is realized in many of the following quaternary sulfur‐containing formulae and structures: M 3 OFS 3 ( M = Er),12 M 3 OF 3 S 2 ( M = Y, Dy – Yb),13 M 3 OF 5 S ( M = Nd, Sm, Gd – Ho),14,15 and M 6 O 2 F 8 S 3 ( M = La – Nd, Sm, Gd) 16. Closely related are most of the analogous selenium compounds.…”

“…Although the lanthanum compound La 2 OF 2 Se17 shows the same stoichiometry, it forms a different structure for a better differentiation called A‐type. In addition, we were recently able to synthesize further related compounds like Sm 5 OF 5 Se 4 ,18 Ce 6 O 4 F 4 Se 3 ,19 Ho 3 OFSe 3 , and Ho 3 OF 3 Se 2 ,20 which sometimes do have sulfide analogues (Er 3 OFS 3 and Er 3 OF 3 S 2 12).…”