Crystals 2012, 2(3), 1136-1145; doi:10.3390/cryst2031136

Article
The Short Series of the Oxygen-Poor Lanthanide Oxide Selenides M10OSe14 with M = La–Nd
Frank A. Weber , Christian M. Schurz , Susanne Frunder , Charlotte F. Kuhn and Thomas Schleid *
Institute for Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, Stuttgart D-70569, Germany; Email: f.a.weber@freenet.de (F.A.W.); schurz@iac.uni-stuttgart.de (C.M.S.); susanne.wunderle@uni-hohenheim.de (S.F.); kuhn@iac.uni-stuttgart.de (C.F.K.)
*
Authors to whom correspondence should be addressed; Email: schleid@iac.uni-stuttgart.de; Tel.: +49-711-6856-4240; Fax: +49-711-6856-4241.
Received: 6 June 2012; in revised form: 6 July 2012 / Accepted: 17 July 2012 /
Published: 16 August 2012

Abstract

: Single crystals and phase pure samples of oxygen-poor ternary lanthanide oxide selenides with the composition M10OSe14 (M = La–Nd; tetragonal, I41/acd; a = 1592.0–1559.8 pm, c = 2106.5–2062.9 pm) could be obtained by reacting the corresponding metals, selenium and selenium dioxide as oxygen source. Their crystal structures are isotypic with Pr10OS14 and thus contain isolated [OM4]10+ tetrahedra (d(O2-M3+) = 243–248 pm) embedded in a complex anionic Crystals 02 01136 i001 {[M6Se14]10–} lanthanide selenide matrix (d(M3+-Se2-) = 288-358 pm). All three crystallographically independent M3+ cations exhibit eight contacts to chalcogenide anions (O2– and/or Se2–) resulting in the formation of bicapped trigonal prismatic coordination polyhedra. The optical band gaps of the oxide selenides M10OSe14 amount to values between 1.89 and 2.04 eV indicating wide band-gap semiconductors.
Keywords:
lanthanides; oxide selenides; crystal structures; band gaps; synthesis

1. Introduction

Up to now many oxide selenides of the trivalent lanthanides with four different compositions, but five structure types, are known to literature: M10OSe14 (M = La, Pr) [1,2,3], M2OSe2-I (M = Gd) [4], M2OSe2-II (M = Pr) [1,2], M2O2Se (M = La, Pr, Nd, Sm, Gd, Er, Ho, Yb, Lu) [1,2,5] and M4O4Se3 (M = La–Nd, Sm) [1,2,6,7]. Oxide centered metal tetrahedra [OM4]10+ represent the dominating structural feature of all, but occurs as isolated entities just in the M10OSe14-type compounds. While the M2OSe2-I-type representatives exhibit their condensation to a chain via common cis-oriented edges, the remaining three examples show different kinds of layers built up of these [OM4]10+ tetrahedra also by vertex- and edge-condensation. Furthermore, selenide and diselenide anions coexist in the crystal structure of the M4O4Se3-type compounds according to M4O4Se[Se2]. The title compounds M10OSe14 (M = La–Nd) follow up and suffer from the same kind of problem as the homologous oxide sulfides M10OS14 [8,9]: Both were formerly addressed as B-type modifications of the corresponding lanthanide sesquichalcogenides M2Ch3 (Ch = S and Se) [10,11]. Besançon and coworkers [12,13] have refined Pr10OS14 as first example of this structure type. More recently, Meerschaut et al. [14] refined a structure model for La10O0.945Se14.055 with a mixed occupation of O2- and Se2- anions at a common Wyckoff position (8a), which raises some questions. We are now presenting the crystal structures of the complete short M10OSe14 series with M = La–Nd here. A comment on La10O0.945Se14.055 is given as well as a detailed comparison between the title compounds and the isostructural lanthanide oxide sulfides M10OS14 (M = La–Nd, Sm, Gd) [8,9]. Furthermore, we compare the optical band gaps of the title compounds with those of the C-type sesquiselenides of the lanthanides M2Se3 and the oxide selenide diselenides M4O4Se[Se2].

2. Results and Discussion

2.1. Structure Description

The oxygen-poor ternary lanthanide oxide selenides M10OSe14 crystallize with the Pr10OS14-type structure [12,13] in the tetragonal system with the space group I41/acd (no. 142) and eight formula units per unit cell (M = La: a = 1592.04(9) pm, c = 2106.48(14) pm; M = Ce: a = 1578.96(9) pm, c = 2086.59(14) pm; M = Pr: a = 1568.74(8) pm, c = 2073.42(13) pm; M = Nd: a = 1559.83(8) pm, c = 2062.91(12) pm). Compared to the lattice constants of La10OSe14 at 153 K (a = 1588.8(2), c = 2101.4(3) pm) [3] and within all expectations, the lattice parameters presented here show slightly larger values than those subjected to the X-ray experiments at room temperature (298 K).

Eight crystallographically independent atoms (see Table 1) reside at four different Wyckoff positions: O at 8a (site symmetry: Crystals 02 01136 i002..), Se4 at 16e (.2.), M3 at 16f (..2) along with M1, M2, Se1, Se2 and Se3 all at the general 32g site with symmetry 1. The coordination spheres of the trivalent lanthanide cations M3+ exhibit a trigonal prismatic shape with two caps each (see Figure 1). From these, just (M2)3+ binds the light O2– anion apart from seven contacts to Se2–, while (M1)3+ and (M3)3+ show eight bonds to only Se2– anions.

Crystals 02 01136 g001 200
Figure 1. View of the coordination spheres of the trivalent lanthanide cations (a) (M1)3+; (b) (M2)3+; and (c) (M3)3+ in the crystal structure of the M10OSe14 representatives (M = La–Nd).

Click here to enlarge figure

Figure 1. View of the coordination spheres of the trivalent lanthanide cations (a) (M1)3+; (b) (M2)3+; and (c) (M3)3+ in the crystal structure of the M10OSe14 representatives (M = La–Nd).
Crystals 02 01136 g001 1024
Table 1. Fractional atomic coordinates for the four M10OSe14 representatives with M = La–Nd.

Click here to display table

Table 1. Fractional atomic coordinates for the four M10OSe14 representatives with M = La–Nd.
Atomx/ay/bz/cAtomx/ay/bz/c
La10OSe14Pr10OSe14
La132g0.13003(4)0.02695(4)0.04721(2)Pr132g0.12991(3)0.02686(3)0.04742(2)
La232g0.37036(4)0.25434(4)0.05965(2)Pr232g0.37071(3)0.25436(3)0.05951(2)
La316f0.13330(4)x + 1/41/8Pr316f0.13364(4)x + 1/41/8
O8a01/43/8O8a01/43/8
Se132g0.02192(6)0.38134(7)0.00124(4)Se132g0.02218(5)0.38111(5)0.00199(4)
Se232g0.34224(7)0.07046(7)0.09270(4)Se232g0.34290(5)0.07081(5)0.09262(4)
Se332g0.03914(6)0.07100(7)0.17174(4)Se332g0.03885(5)0.07057(5)0.17167(4)
Se416e0.35523(9)01/4Se416e0.35463(7)01/4
Ce10OSe14Nd10OSe14
Ce132g0.13000(3)0.02686(3)0.04741(2)Nd132g0.12963(3)0.02694(3)0.04743(2)
Ce232g0.37049(3)0.25428(3)0.05949(2)Nd232g0.37075(3)0.25459(3)0.05933(2)
Ce316f0.13347(3)x + 1/41/8Nd316f0.13381(3)x + 1/41/8
O8a01/43/8O8a01/43/8
Se132g0.02201(4)0.38106(5)0.00168(3)Se132g0.02249(5)0.38122(5)0.00236(4)
Se232g0.34256(5)0.07063(5)0.09262(3)Se232g0.34298(5)0.07106(5)0.09269(4)
Se332g0.03891(5)0.07076(5)0.17178(3)Se332g0.03876(5)0.07060(5)0.17159(4)
Se416e0.35487(6)01/4Se416e0.35395(7)01/4

All important interatomic distances (Table 2) are very similar to those found in other well-investigated compounds (Table 3). According to the oxygen implementation, the Se2–M3+ distance ranges expands largely from the C-type M2Se3 to the M10OSe14compounds (Table 2 and Table 3). Regarding the significantly different distances between O2–/Se2– and (M2)3+ (243–248 pm vs. 288–348 pm) the refinement of a mixed site occupation of O2– and Se2– at the Wyckoff position 8a just like in La10O0.945Se14.055 [14] is certainly not appropriate.

Table 2. Important internuclear distances (d/pm) for the four M10OSe14 representatives (M = La–Nd).

Click here to display table

Table 2. Important internuclear distances (d/pm) for the four M10OSe14 representatives (M = La–Nd).
M10OSe14M = LaM = CeM = PrM = Nd
M1–Se1(1×)298.7(1)296.4(1)294.4(1)292.4(1)
–Se4(1×)301.1(1)298.2(1)296.2(1)294.1(1)
–Se2(1×)306.0(1)303.4(1)301.5(1)300.2(1)
–Se1'(1×)306.2(1)304.2(1)302.2(1)300.2(1)
–Se3(1×)307.7(1)304.7(1)302.5(1)300.6(1)
–Se2'(1×)309.8(1)307.1(1)305.4(1)303.8(1)
–Se3'(1×)310.0(1)307.9(1)306.1(1)304.6(1)
–Se2''(1×)357.9(1)355.4(1)353.8(1)352.4(1)
M2–O(1×)248.2(1)246.1(1)244.2(1)243.0(1)
–Se1(1×)294.5(1)291.9(1)289.9(1)288.0(1)
–Se2(1×)304.2(1)301.4(1)299.2(1)297.6(1)
–Se3(1×)308.8(1)305.6(1)304.1(1)302.4(1)
–Se3'(1×)314.9(1)312.0(1)310.1(1)308.6(1)
–Se4(1×)320.1(1)317.9(1)316.3(1)314.9(1)
– Se2'(1×)329.1(1)326.2(1)323.6(1)321.6(1)
–Se1'(1×)348.3(1)345.3(1)343.3(1)342.2(1)
M3–Se3(2×)300.6(1)298.1(1)296.2(1)294.5(1)
–Se2(2×)308.1(1)305.6(1)303.4(1)301.8(1)
– Se1(2×)315.3(1)311.8(1)309.3(1)306.9(1)
– Se4(2×)322.8(1)319.7(1)317.5(1)315.8(1)
Table 3. Selected internuclear distances (d/pm) and angles (∢/deg) for the M10OSe14representatives (M = La–Nd) in comparison to those for known related compounds (in italics).

Click here to display table

Table 3. Selected internuclear distances (d/pm) and angles (∢/deg) for the M10OSe14representatives (M = La–Nd) in comparison to those for known related compounds (in italics).
Distances/angles/examplesLa10OSe14Ce10OSe14Pr10OSe14Nd10OSe14
d(Se2–M3+)295–358292–355290–354288–352
example 1C-La2Se3 [15]C-Ce2Se3 [16]C-Pr2Se3 [15]C-Nd2Se3 [17]
304–323302–320299–318297–317
example 2La5NSe6 [18]Ce3ONSe2 [19]Pr2OSe2 [1]Nd3ONSe2 [19]
289–355 293–355293–331289–347
d(O2–M3+)(4×)248.2246.1244.2243.0
exampleLa10OS14 [8]Ce10OS14 [8]Pr10OS14 [8]Nd10OS14 [8]
245.4243.0242.1240.8
M2-O-M2 (4×)107.9108.0108.0108.1
M2-O-M2' (2×)112.6112.5112.4112.2
exampleLa10OS14 [8]Ce10OS14 [8]Pr10OS14 [8]Nd10OS14 [8]
∢M2-O-M2 (4×)108.1108.2108.2108.3
∢M2-O-M2' (2×)112.3112.1112.1111.9

Isolated oxide-anion centered metal tetrahedra [O(M2)4]10+ (Figure 2b) embedded in a complex anionic lanthanide selenide matrix Crystals 02 01136 i001 {[(M1)3(M3)3Se14]10–} dominate the crystal structure of the title compounds (Figure 2a). The distances between O2– and (M2)3+ in these oxide selenides M10OSe14 decrease from 248 pm for M = La to 243 pm for M = Nd caused by the lanthanide contraction, but they also amount to values slightly higher than in the corresponding lanthanide oxide sulfides M10OS14 (Table 3, M = La–Nd). Although most trends remain the same in the oxide chalcogenides M10OCh14 from M = La to M = Nd, the angles M2-O-M2 exhibit lower values in the selenide compounds, while the angles M2-O-M2' show higher values as compared to the sulfide representatives. These effects certainly originate from the different sizes of the chalcogenide anions within the complex anionic lanthanide chalcogenide matrix Crystals 02 01136 i001 {[(M1)3(M3)3Ch14]10–} (S2–vs. Se2–). Similar to the M10OS14-type compounds (M = La-Nd, Sm and Gd) [8,9], most of the oxygen-free part in this crystal structure of the M10OSe14 series (M10Se14M2Se2.8, M = La–Nd) can be interpreted as closely related to the cation-defective Th3P4-type structure [20] of the corresponding lanthanide sesquiselenides M2Se3 known as their C-type modification [15,16,17]. Hence the internuclear distances between Se2– and M3+ do not differ significantly, with the exception of the contacts M1-Se2'' and M2-Se1' in the title compounds (compare Table 2 and Table 3).

Crystals 02 01136 g002 200
Figure 2. View at (a) the unit-cell representation; and (b) the isolated [O(M2)4]10+ tetrahedrawith their full Se2– surrounding in the crystal structure of the M10OSe4 representatives (M = La–Nd).

Click here to enlarge figure

Figure 2. View at (a) the unit-cell representation; and (b) the isolated [O(M2)4]10+ tetrahedrawith their full Se2– surrounding in the crystal structure of the M10OSe4 representatives (M = La–Nd).
Crystals 02 01136 g002 1024

2.2. Optical Band Gaps

The optical band gaps of the oxide selenides M10OSe14 amount to values between 1.89 eV and 2.04 eV (see Table 4 and Figure 3), so they should represent typical semiconducting materials. In comparison with the oxygen-richer oxide selenide diselenides M4O4Se[Se2] the band gaps are exhibiting lower values than those of the title compounds. Similar to the M4O4Se[Se2] series the transitions of electrons from the 4f to the 5d orbitals or within the 4f shell of the lanthanides in the related M10OSe14 representatives can be detected below the actual band gap for the corresponding cerium (mainly 4f–5d), praseodymium and neodymium compounds (mainly intra 4f).

Table 4. Comparison of the optical band gaps of the M10OSe14, M4O4Se[Se2] and C-M2Se3 representatives (M = La–Nd).

Click here to display table

Table 4. Comparison of the optical band gaps of the M10OSe14, M4O4Se[Se2] and C-M2Se3 representatives (M = La–Nd).
General formulaReferenceM = LaM = CeM = PrM = Nd
M10OSe14this work2.04 eV1.97 eV1.89 eV1.98 eV
M4O4Se[Se2] [7]1.89 eV1.69 eV1.87 eV1.87 eV
M2Se3 [21]2.3 eV1.85 eV2.0 eV2.0 eV
Crystals 02 01136 g003 200
Figure 3. Diffuse reflectance spectra (DRS) of the M10OSe14 representatives (M = La–Nd) after applying a Kubelka-Munk transformation.

Click here to enlarge figure

Figure 3. Diffuse reflectance spectra (DRS) of the M10OSe14 representatives (M = La–Nd) after applying a Kubelka-Munk transformation.
Crystals 02 01136 g003 1024

Strobel et al. [7] interpret the conduction band (CB) as predominately an attribute of the 4p states of Se and the valence band (VB) as the main attribute of the empty 5d orbitals of the respective lanthanides. This should be also true for the oxide selenides M10OSe14. But the differences in the crystal structures (tetragonal for M10OSe14 vs. orthorhombic for M4O4Se3) and the different kinds of selenide units (Se2– in M10OSe14 vs. Se2– and [Se2]2– in M4O4Se3) cause some variations in the optical band gaps. While for the title compounds just the eightfold coordination is realized for the trivalent lanthanide cations, the M4O4Se3 representatives exhibit eight- as well as sixfold coordination spheres for these cations. More importantly, the diselenide units [Se2]2– in the M4O4Se3 cases probably shift the band gaps to significantly smaller values as the bonding situation and therefore the energy levels of VB should be quite different from those examples with just Se2– anions (M2Se3 and M10OSe14). All these band gaps are somewhat lower than those of the C-type lanthanide sesquiselenides M2Se3 with M = La–Nd investigated by Prokofiev et al. [21] (1.85–2.30 eV), but they clearly support a strong similarity between all these selenide representatives (M2Se3, M10OSe14 and M4O4Se[Se2]). Furthermore, it opens not only for the oxide selenides with the general formula M10OSe14 (M = La–Nd) but a new scientific field for their applications as red pigments without toxic metals like cadmium [22].

3. Experimental Section

Single crystals and phase pure samples of the M10OSe14 representatives with M = La–Nd were obtained after heating mixtures of the respective lanthanide metal (ChemPur: 99.9%), selenium (Merck: 99.9%) and selenium dioxide (SeO2, ChemPur: 99.999%) in molar ratios of 20:27 : 1 along with an excess of caesium chloride (CsCl, ChemPur: 99.9%) as flux at 800 °C for four days in evacuated silica ampoules according to:

20 M + 27 Se + SeO2 → 2 M10OSe14

For crystals of high quality, these mixtures had to be cooled within four days from 800 to 500 °C followed by a subsequent slow cooling process down to room temperature within ten hours.

All four water- and air-stable products were characterized by single-crystal X-ray diffraction (IPDS-I, Stoe, Mo-Kα radiation with graphite monochromator: λ = 71.01 pm) at room temperature. Essential information for the structure solutions and refinements for the representatives of the M10OSe14 series (M = La–Nd) using the program packages SHELXS-97 and SHELX-97 [23] as well as X-RED (within X-SHAPE) for correction of absorption [24] and scattering factors from the International Tables (Volume C) [25] is available from Table 5. Further details can be obtained from the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen, Germany, on quoting the depository numbers CSD-424095 (La10OSe14), CSD-424094 (Ce10OSe14), CSD-94413 (Pr10OSe14), and CSD-424093 (Nd10OSe14).

Table 5. Crystallographic data for the four M10OSe14 representatives (M = La–Nd).

Click here to display table

Table 5. Crystallographic data for the four M10OSe14 representatives (M = La–Nd).
M10OSe14M = LaM = CeM = PrM = Nd
Colourredruby redruby redruby red
Crystal systemtetragonaltetragonaltetragonaltetragonal
Space group/Formula unitsI41/acd/Z = 8I41/acd/Z = 8I41/acd/Z = 8I41/acd/Z = 8
a (pm)1592.04(9)1578.96(9)1568.74(8)1559.83(8)
c (pm)2106.48(14)2086.59(14)2073.42(13)2062.91(12)
c/a1.3231.3211.3221.322
Vm (cm3/mol)/Dx (g/cm3)401.91/6.247391.60/6.442384.11/6.588377.83/6.786
F(000)/ θmax8432/30.28512/31.68592/30.48672/31.6
±h/±k/±l22/22/2923/23/3022/22/2922/22/30
Reflections (all/independent)36621/199952742/217843025/192639083/2117
μ/mm–134.7036.6938.6640.58
Rint/Rσ0.118/0.0510.127/0.0470.101/0.0340.087/0.026
R1/wR20.069/0.0780.066/0.0570.052/0.0670.059/0.096
GooF0.9860.9730.9861.037

Diffuse reflectance spectra (DRS) were recorded on a TIDAS UV-VIS-spectrometer (J&M) equipped with optic fibers. As reference, a Ba[SO4] standard found application. For converting the reflectance into absorbance and obtaining the band gap information, the Kubelka-Munk function was applied. This approximation relates the absorbance coefficient (α) and the diffusion coefficient (S) of the compounds. The absorption-edge energies (Eg) were derived by the intersection points of the particular baseline along the energy axis and the extrapolated line of the linear part of the threshold.

4. Conclusions

The crystal structures of all four representatives of the oxide selenides M10OSe14 with M = La–Nd exhibit the Pr10OS14-type arrangement. Hence, the lanthanide selenide matrix Crystals 02 01136 i001 {[(M1)3(M3)3Se14]10–} embed isolated [O(M2)4]10+ tetrahedra. It should be noted that no hint of the existence of representatives with heavier lanthanides (M = Sm–Lu) could be obtained so far, but we are still busy trying to synthesize them. The optical band gaps amount to values between 1.89 and 2.04 eV encouraging investigations in their ability to be used for application as red pigments. Based on the interplay of the light anions O2– and N3– in the perovskite-type compounds Ca(1–x)LaxTaO(2–x)N(1+x) [26], we are also actively investigating the band-gap changes in correlation with nitride incorporation in this structure type represented by the recently published compound La10.25O0.25N0.75Se14 [27,28].

Acknowledgments

The authors want to thank Falk Lissner for the X-ray diffraction data collection and Sabine Strobel for the DRS data collection. This research was supported by the federal state of Baden-Württemberg (Stuttgart) and the Deutsche Forschungsgemeinschaft (DFG, Bonn).

References

  1. Weber, F.A.; Schleid, T. Vier oxidselenide des praseodyms: Pr10OSe14, Pr2OSe2, Pr2O2Se und Pr4O4Se3 (In German). Z. Anorg. Allg. Chem. 2001, 627, 1383–1388, doi:10.1002/1521-3749(200106)627:6<1383::AID-ZAAC1383>3.0.CO;2-F.
  2. Weber, F.A. Präparative Studien in den Mehrstoffsystemen Selten-Erd-Metall–Selen bzw. Tellur und Sauerstoff (In German). Ph.D. Dissertation, University of Stuttgart, Stuttgart, Germany, 1999.
  3. Li, B.W.; Huang, F. Refinement of the crystal structure of decalanthanum monooxide tetradecaselenide La10OSe14 at 153 K. Z. Kristallogr. New Cryst. Struct. 2007, 222, 175–176.
  4. Tougaît, O.; Ibers, J.A. Gd2OSe2. Acta Crystallogr. 2000, A56, 623–624.
  5. Eick, H.A. The crystal structures and lattice parameters of some rare earth mono-seleno oxides. Acta Crystallogr. 1960, 13, 161, doi:10.1107/S0365110X60000339.
  6. Dugué, J.; Adolphe, C.; Khodadad, P. Structure cristalline de l’oxyséléniure de lanthane La4O4Se3 (In French). Acta Crystallogr. 1970, B26, 1627–1628.
  7. Strobel, S.; Choudhury, A.; Dorhout, P.K.; Lipp, C.; Schleid, T. Rare-earth metall(III) oxide selenides M4O4Se[Se2] (M = La, Ce, Pr, Nd, Sm) with discrete diselenide units: Crystal structures, magnetic frustration and other properties. Inorg.Chem. 2008, 47, 4936–4944, doi:10.1021/ic800233c.
  8. Schleid, T.; Lissner, F. M10S14O-type oxysulphides (M ≡ La, Ce, Pr, Nd, Sm) as an “oxygen trap” in oxidation reactions of reduced lanthanide chlorides with sulphur. J. Less Common Met. 1991, 175, 309–319, doi:10.1016/0022-5088(91)90017-X.
  9. Schleid, T.; Weber, F.A. Crystal structure of dekagadolinium(III) oxide tetradekasulfide, Gd10OS14. Z. Kristallogr. New Cryst. Struct. 1998, 213, 32.
  10. Picon, M.; Domange, L.; Flahaut, J.; Guittard, M.; Patrie, M. Les sulfures Me2S3 et Me3S4 des elements des TerresRares (In French). Bull. Soc. Chim. Fr. 1960, 1960, 221–228.
  11. Flahaut, J. Les Éléments des Terres Rares, Collection de Monographies de Chimie (In French); Masson: Paris, France, 1969; p. 127.
  12. Carré, D.; Laurelle, P.; Besançon, P. Structure cristalline de la prétenduevariété β des sulfures de terres rares de composition Pr10S14O (In French). C. R. Hebd. Seances Acad. Sci. 1970, C270, 537–539.
  13. Besançon, P. Teneur en oxygéne et formule exacte d’Une famille de composés habituellement appelés “variété β” ou “phase complexe” des sulfures de terres rares (In French). J. Solid State Chem. 1973, 7, 232–240, doi:10.1016/0022-4596(73)90159-X.
  14. Meerschaut, A.; Lafond, A.; Palvadeau, P.; Deudon, C.; Cario, L. Synthesis and crystal structure of two new oxychalcogenides: Eu5V3S6O7 and La10Se14O. Mater. Res. Bull. 2002, 37, 1895–1905, doi:10.1016/S0025-5408(02)00883-8.
  15. Folchnandt, M.; Schleid, T. Single crystals of C-La2Se3, C-Pr2Se3 and C-Gd2Se3 with cation-deficient Th3P4-type structure. Z. Anorg. Allg. Chem. 2001, 627, 1411–1413, doi:10.1002/1521-3749(200107)627:7<1411::AID-ZAAC1411>3.0.CO;2-X.
  16. Folchnandt, M.; Schneck, C.; Schleid, T. Über Sesquiselenide der Lanthanoide: Einkristalle von Ce2Se3 im C-, Gd2Se3 im U- und Lu2Se3 im Z-Typ (In German). Z. Anorg. Allg. Chem. 2004, 630, 149–155, doi:10.1002/zaac.200300266.
  17. Schneck, C.; Höss, P.; Schleid, T. C-type Nd2Se3. ActaCrystallogr. 2009, 65, i20.
  18. Schurz, C.M.; Lissner, F.; Janka, O.; Schleid, T. Synthese und kristallstruktur der N3–-armen Nitridselenide des Formeltyps M5NSe6 (M = La–Pr) mit isolierten Tetraederdoppeln [N2M6]12+ (In German). Z. Anorg. Allg. Chem. 2011, 637, 1045–1051, doi:10.1002/zaac.201100033.
  19. Lissner, F.; Schleid, T. Die Oxidnitridselenide M3ONSe2 dreiwertiger Lanthanide (M = Ce–Nd) (In German). Z. Anorg. Allg. Chem. 2008, 634, 2799–2804, doi:10.1002/zaac.200800245.
  20. Meisel, K. Kristallstrukturen von thoriumphospiden (In German). Z. Anorg. Allg. Chem. 1939, 240, 300–312, doi:10.1002/zaac.19392400403.
  21. Prokofiey, A.V.; Shelykh, A.I.; Golubkov, A.V.; Smirnov, I.A. Crystal growth and optical properties of rare earth sesquiselenides and sesquisulphides—New magneto-optic materials. J. Alloys Compds. 1995, 219, 172–175, doi:10.1016/0925-8388(94)05058-9.
  22. Wirth, W.; Gloxhuber, C. Toxikologie (In German), 5th ed.; Urban and Fischer: München, Germany, 2000.
  23. Sheldrick, G.M. A short history of SHELX. Acta Crystallogr. 2008, A64, 112–122.
  24. Herrendorf, W.; Bärnighausen, H. HABITUS: A Program for the Optimization of the Crystal Shape for Numerical Absorption Correction in X-SHAPE, Version 1.06; Darmstadt: Karlsruhe, Germany, 1996.
  25. Hahn, T.; Wilson, A.J.C. International Tables for Crystallography, Volume C, 2nd ed.; Kluwer Academic Publishers: Boston, MA, USA, 1992.
  26. Jansen, M.; Letschert, H.P. Inorganic yellow-red pigments without toxic metals. Nature 2000, 404, 980–982, doi:10.1038/35010082.
  27. Schurz, C.M.; Schleid, T. La10.25O0.25N0.75Se14: The first lanthanum oxide nitride selenide with a stuffed Pr10OS14-Type structure and subtle interactions of La3+ Cations. Z. Kristallogr. 2012, 104.
  28. Schurz, C.M. Über Nitridhalogenide und -Chalkogenide Dreiwertiger Seltenerdmetalle: Synthese, Kristallstrukturen, Optische Spektroskopie und Oxidische Derivate (In German). Ph.D. Dissertation, University of Stuttgart, Stuttgart, Germany, 2011.
Crystals EISSN 2073-4352 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert