Co-reporter:K. Kaspar;K. Fritsch;K. Habicht;B. Willenberg
Journal of Electronic Materials 2017 Volume 46( Issue 1) pp:92-100
Publication Date(Web):2017 January
DOI:10.1007/s11664-016-4820-y
In this study we show a preparation method for nanostructured Bi0.85Sb0.15 powders via a chemical reduction route in a polyol medium, yielding material with particle sizes of 20–150 nm in scalable amounts. The powders were consolidated by spark plasma sintering (SPS) in order to maintain the nanostructure. To investigate influence of the sinter process, the powders were characterized by x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), and scanning electron microscopy (SEM) measurements before and after SPS. Transport properties, Seebeck effect, and thermal conductivity were determined in the low temperature range below 300 K. The samples showed excellent thermal conductivity of 2.3–2.6 W/m × K at 300 K and Seebeck coefficients from −97 μV/K to −107 μV/K at 300 K with a maximum of −141 μV/K at 110 K, thus leading to ZT values of up to 0.31 at room temperature. The results show that Bi-Sb-alloys are promising materials for low-temperature applications. Our wet chemical approach gives access to scalable amounts of nano-material with increased homogeneity and good thermoelectric properties after SPS.
Co-reporter:Sarah Hirt, Fang Yuan, Yurij Mozharivskyj, and Harald Hillebrecht
Inorganic Chemistry 2016 Volume 55(Issue 19) pp:9677-9684
Publication Date(Web):September 13, 2016
DOI:10.1021/acs.inorgchem.6b01467
AlFe2B2 and AlFe2–xCoxB2 (x = 0–0.30) were synthesized from the elements in three different ways. The samples were characterized by powder X-ray diffraction, Rietveld refinements, energy-dispersive X-ray spectroscopy, and magnetic measurements. Using Al flux the formation of AlFe2B2 single crystals is preferred. Arc melting enables the substitution of ∼6% Co. This substitution of Fe by Co decreases the Curie temperature TC from 290 to 240 K. The highest Co substitution up to 15% is achieved by spark plasma sintering (SPS). TC is reduced to 205 K. In all cases an excess of Al is necessary to avoid the formation of ferromagnetic FeB. Al13Fe4–xCox is the common byproduct. TC and the cobalt content are linearly correlated. The transition paramagnetic–ferromagnetic remains sharp for all examples. The magnetic entropy change of the Co-containing samples is comparable to AlFe2B2. SPS synthesis yields, in short reaction times, a homogeneous and dense material with small amounts of paramagnetic Al13Fe4–xCox as an impurity, which can serve as sinter additive. These properties make AlFe2–xCoxB2 a promising magnetocaloric material for applications between room temperature and 200 K.
Co-reporter:Martin Ade and Harald Hillebrecht
Inorganic Chemistry 2015 Volume 54(Issue 13) pp:6122-6135
Publication Date(Web):June 12, 2015
DOI:10.1021/acs.inorgchem.5b00049
Single crystals of the ternary borides Cr2AlB2, Cr3AlB4, Cr4AlB6, MoAlB, WAlB, Mn2AlB2, and Fe2AlB2 were grown from the elements with an excess of Al. Structures were refined by X-ray methods on the basis of single crystal data. All compounds crystallize in orthorhombic space groups. In each case boron atoms show the typical trigonal prisms BM6. The BM6-units are linked by common rectangular faces forming B–B-bonds. Thus, zigzag chains of boron atoms are obtained for MoAlB, WAlB, and M2AlB2 (M = Cr, Mn, Fe); chains of hexagons for Cr3AlB4; and double chains of hexagons for Cr4AlB6. The same subunits are known for the binary borides CrB, Cr3B4, Cr2B3, and β-WB, too. The boride partial structures are separated by single layers of Al-atoms in the case of the chromium compounds and double layers for WAlB, i.e., W2Al2B2. All crystal structures can be described using a unified building set principle with quadratic 44-nets of metal atoms. The different compositions and crystal structures are obtained by different numbers of metal layers in the corresponding parts according to the formula (MB)2Aly(MB2)x. This principle is an extension of a scheme which was developed for the boridecarbides of niobium. Furthermore, there is a close similarity to the group of ternary carbides MAl(MC)n, so-called MAX-phases. Therefore, they might be named as “MAB-phases”. The pronounced two-dimensionality and the mixture of strong covalent and metallic interactions make MAB-phases to promising candidates for interesting material properties. All compositions were confirmed by EDX measurements. Additionally, microhardness measurements were performed.
Co-reporter:Michael Daub, Harald Scherer, and Harald Hillebrecht
Inorganic Chemistry 2015 Volume 54(Issue 5) pp:2325-2330
Publication Date(Web):February 19, 2015
DOI:10.1021/ic502916j
The first mixed-valent boroseleniteselenate B2Se3O10 was obtained as a colorless, hygroscopic compound from the reaction of boric acid (H3BO3) in concentrated selenic acid (H2SeO4) at 265 °C. H2SeO4 can be replaced by appropriate amounts of SeO2 and H2O2. The crystal structure was determined from single-crystal data (P21/c, Z = 4, a = 4.3466(2) Å, b = 7.0237(4) Å, c = 22.1460(9) Å, β = 94.922(2)°, R1 = 0.036, wR2 = 0.096). It represents a new structure type that is characterized by a 3D net of BO4 tetrahedra, SeVIO4 tetrahedra, and trigonal-pyramidal SeIVO3 in a ratio of 2:1:2. 77Se magic-angle-spinning NMR investigations confirm the mixed-valent character because the chemical shifts are found in the typical regions, i.e., 1278 and 1202 ppm for SeIV and 972 ppm for SeVI. The vibrational spectra show the typical modes according to the present polyhedra. In addition, NMR and vibrational spectra of the closely related B2Se2O7 are presented.
Co-reporter:Dr. Michael Daub;Dr. Harald Hillebrecht
Angewandte Chemie International Edition 2015 Volume 54( Issue 38) pp:11016-11017
Publication Date(Web):
DOI:10.1002/anie.201506449
Co-reporter:Dr. Michael Daub;Dr. Harald Hillebrecht
Angewandte Chemie 2015 Volume 127( Issue 38) pp:11168-11169
Publication Date(Web):
DOI:10.1002/ange.201506449
Co-reporter:Michael Daub;Dr. Harald Hillebrecht
Chemistry - A European Journal 2015 Volume 21( Issue 1) pp:298-304
Publication Date(Web):
DOI:10.1002/chem.201404100
Abstract
The first boroselenates were obtained as single crystals by the reaction of selenic acid with boron acid and the corresponding alkali carbonates. The structure determinations showed a far-reaching analogy to very recently described borosulfates and the borophosphates, that is, tetrahedral BO4 and SeO4 units linked by common corners. In each case, the BO4 tetrahedra are surrounded by SeO4 tetrahedra. As a function of the B/Se ratio, this results in chains (1:3; Cs3[B(SeO4)3], Rb3[B(SeO4)3]), isolated pentamers (1:4; HK4[(B(SeO4)4]), or pentamers with additional isolated SeO4 tetrahedra (1:5; (H3O)Na6[B(SeO4)4](SeO4). Compound Rb3[B(SeO4)3] (orthorhombic, Ibca, Z=8, a=7.508(2), b=15.249(3), c=23.454(5) Å) is isotypic to Rb3[B(SO4)3]) and Ba3[B(PO4)3]. Compound Cs3[B(SeO4)3] (monoclinic, P21/c, Z=4, a=11.3552(4), b=7.9893(3), c=15.7692(6) Å, β=101.013(1)°) represents a distorted variant of Rb3[B(SeO4)3]. The isolated pentamers in HK4[(B(SeO4)4]) (triclinic, P, Z=6, a=7.5303(1), b=7.5380(1), c=42.3659(4) Å, α=88.740(1), β=89.971(1), γ=89.971(1)°) were also found in K5[(B(SO4)4] and Na5[(B(SO4)4]. Compound (H3O)Na6[B(SeO4)4](SeO4) (tetragonal, I, a=9.9796(1), c=18.2614(2) Å) is a super structure of the borophosphates Sr6[B(PO4)4](PO4) and Pb6[B(PO4)4](PO4). Because the tetrahedra are only connected through apices, there are topological analogies to silicates. Therefore, boroselenates may have a similar variability of crystal structures, such as borosulfates and borophosphates.
Co-reporter:Michael Daub, Karolina Kazmierczak, Peter Gross, Henning Höppe, and Harald Hillebrecht
Inorganic Chemistry 2013 Volume 52(Issue 10) pp:6011-6020
Publication Date(Web):May 8, 2013
DOI:10.1021/ic400267s
New alkali borosulfates were obtained by precipitation from oleum, solid-state reactions, or thermal decomposition. The crystal structures were characterized with single-crystal data. They are all based on corner-linked BO4 and SO4 tetrahedra with varying coordination of the alkali cations. According to the ratio of BO4 and SO4 tetrahedra, different frameworks are observed, i.e., noncondensed complex anions (1:4), one-dimensional chains (1:3), or three-dimensional (3D) networks (1:2). This is in analogy to silicates, where the ratio Si/O relates to the dimensionality also. For Na5[B(SO4)4], which exists in two different polymorphs, there are noncondensed pentameric units. Na5[B(SO4)4]-I: space group Pca21, a = 10.730(2) Å, b = 13.891(3) Å, c = 18.197(4) Å. Na5[B(SO4)4]-II: space group P212121, a = 8.624(2) Å, b = 9.275(2) Å, c = 16.671(3) Å. A3[B(SO4)3] (A = K, Rb) are isotypic with Ba3[B(PO4)3] adopting space group Ibca [K3[B(SO4)3], a = 7.074(4) Å, b = 14.266(9) Å, c = 22.578(14) Å; Rb3[B(SO4)3], a = 7.2759(5) Å, b = 14.7936(11) Å, c = 22.637(2) Å] with vierer chains of BO4tetrahedra based on two bridging and two terminal SO4 tetrahedra. Li[B(SO4)2] [space group Pc, a = 7.6353(15) Å, b = 9.342(2) Å, c = 8.432(2) Å, and β = 92.55(2)°] comprises a 3D network that is closely related to β-tridymite. Li[B(S2O7)2] [space group P212121, a = 10.862(2) Å, b = 10.877(2) Å, c = 17.769(4) Å] represents the first example of a disulfate complex with noncondensed [B(S2O7)2]− units. Vibrational spectra were recorded from all compounds, and the thermal behavior was also investigated.
Co-reporter:Peter Schultz, Vanessa Sagawe, Harald Hillebrecht
Solid State Sciences 2013 Volume 26() pp:121-127
Publication Date(Web):December 2013
DOI:10.1016/j.solidstatesciences.2013.10.001
Red single crystals of a hexagonal form of ScAlOC were obtained as a by-product from the synthesis of ScAl3C3 by reacting scandium and carbon in an aluminium melt at 1820 °C. The crystal structure (hP8, space group P63mc, Z = 2, a = 3.24793(3) Å, c = 10.1739(1) Å, 629 refl., 15 param., R1(F) = 0.010, wR2(F2) = 0.023) can directly be derived from the binary nitrides AlN and ScN or the oxide carbides Sc(O,C) and Al(O,C), respectively. ScAlOC-II or h-ScAlOC represents a new structure type with simple closest packing of alternating layers of oxygen and carbon. The stacking sequence is ABAC (=(hc)2) with oxygen in a cubic and carbon in a hexagonal sequence. According to the difference in size Sc occupies octahedral voids between every second layer leading to layers of edge-sharing ScO3C3 octahedra. Aluminium is located in half of the tetrahedral voids. The AlOC3-tetrahedra are connected to layers by common corners of the carbon atoms. h-ScAlOC continues the row of the rare examples of oxide carbides with ordered anion distribution. Band structure calculations by FP-(L)APW methods revealed that ScAlOC is electron precise with a band gap of 1.2 eV. Calculations of charges by the Bader-method reveal values of Sc+1.87, Al+2.33, O−1.52 and C−2.67. Together with the charge densities and the values of the Laplacian this stands for a mainly ionic bonding containing significant covalent contributions, too. Despite the close similarity to rhombohedral ScAlOC (r-ScAlOC) there is a striking difference in colour, as r-ScAlOC is black. This is confirmed and explained by the results of the P-DOS, because the lowest states of the conduction band are determined by Sc-d-states. These are significantly lower in r-ScAlOC with ScC6 and ScO6 octahedra than in h-ScAlOC leading to a calculated band gap of 0.3 eV.
Co-reporter:Dipl.-Chem. Michael Daub;Dr. Karolina Kazmierczak;Dr. Henning A. Höppe;Dr. Harald Hillebrecht
Chemistry - A European Journal 2013 Volume 19( Issue 50) pp:16954-16962
Publication Date(Web):
DOI:10.1002/chem.201303012
Abstract
The structural principles of borosulfates derived from the B/S ratio are confirmed and extended to new representatives of this class showing novel motifs. According to the composition, Na[B(S2O7)2] (P21/c; a=10.949(6), b=8.491(14), c=12.701(8) Å; β=110.227(1)°; Z=4) and K[B(S2O7)2] (Cc; a=11.3368(6), b=14.662(14), c=13.6650(8) Å; β=94.235(1)°; Z=8) contain isolated [B(S2O7)2]− ions, in which the central BO4 tetrahedron is coordinated by two disulfate units. The alkali cations have coordination numbers of 7 (Na) and 8 (K), respectively. The structure of Cs[B(S2O7)(SO4)] (P21/c; a=10.4525(6), b=11.3191(14), c=8.2760(8) Å; β=103.206(1); Z=4) combines, for the first time, sulfate and disulfate units into a chain structure. Cs has a coordination number of 12. The same structural units were found in H[B(S2O7)(SO4)] (P21/c; a=15.6974(6), b=11.4362(14), c=8.5557(8) Å; β=90.334(3)°; Z=8). This compound represents the first example of a polyacid. The hydrogen atoms were located and connect the chains to form layers through hydrogen-bonding bridges. H3O[B(SO4)2] (P4/ncc; a=9.1377(6), c=7.3423(8) Å; Z=4) is the first oxonium compound of this type to be found. The BO4 tetrahedra are linked by SO4 tetrahedra to form linear chains similar to those in SiS2. The chains form a tetragonal rod packing structure with H3O+ between the rods. The structures of borosulfates can be classified following the concept described by Liebau for silicates, which was extended to borophosphates by Kniep et al. In contrast to these structures, borosulfates do not comprise B-O-B bonds but instead contain S-O-S connections. All compounds were obtained as colourless, moisture-sensitive single crystals by reaction of B2O3 and the appropriate alkali salt in oleum.
Co-reporter:Melanie Schroeder ; Sabina Hartwig ; Karl W. Krämer ; Silvio Decurtins
Inorganic Chemistry 2012 Volume 51(Issue 15) pp:8385-8393
Publication Date(Web):July 23, 2012
DOI:10.1021/ic3009442
Black single crystals of the new dodecahalogenotrimetallate In4Ti3Br12 were obtained by reacting InBr3 with Ti-wire at 450 °C in a silica tube sealed under vacuum. In4Ti3Br12 (Pearson symbol hR57, space group R3̅m, Z = 3, a = 7.3992(8) Å, c = 36.673(6) Å, 643 refl., 25 param., R1(F) = 0.025; wR2(F2) = 0.046) is a defect variant of a 12 L-perovskite. In+ cations are 12-fold coordinated in two different ways: In1 as an anticuboctahedron and In2 as a cuboctahedron. In both cases the 5s2 configuration results in 3 short, 6 medium, and 3 long In–Br distances which might be explained as lone pair effect or second order Jahn–Teller instability. Furthermore there are isolated linear trimers [Ti3Br12]4– consisting of facesharing octahedra similar to [Ru3Cl12]4–. The [Ti3Br12]4–-unit has to be described as a mixed-valent d1-d2-d1 system. According to magnetic measurements, the Ti-atoms in In4Ti3Br12 show strong antiferromagnetic interactions (Θ = −1216(6) K) which might be addressed as weak Ti3+–Ti2+–Ti3+ bonds. For comparison, single crystals of K3Ti2X9 (X = Cl, Br) were synthesized and their structures refined. The rotation of the Ti2X93– dimers reduced the symmetry of the well-known Cs3Cr2Cl9 type from P63/mmc to P63/m and resulted in the formation of merohedral twins. According to the unit cell volumes In+ is smaller than K+ in all cases.
Co-reporter:Rainer Lux, Verena Kuntze, Harald Hillebrecht
Solid State Sciences 2012 Volume 14(Issue 10) pp:1445-1453
Publication Date(Web):October 2012
DOI:10.1016/j.solidstatesciences.2012.07.028
Single crystals of the new ternary compound V11Cu9Ga46 were obtained from the elements. Its crystal structure (cP792; Pm 3¯n, a = 23.362(3) Å, 1797 refl., 170 param., wR2(F2) = 0.058) represents a new structure type which is characterized by motifs of the binary V8Ga41 and the ternary V2Cu3Ga8. The first contains centaur-polyhedra VGa10, linked to a super-cube with a cuboctahedrally coordinated Ga-atom in the center. These super-cubes are packed like the atoms of the Cr3Si-type. The arrangement of vanadium-polyhedra around the GaGa12-centers corresponds to the arrangement of metal–atoms in γ-brass. The second structural element represents a defect- and ordering variant of a bcc packing or CsCl, respectively. The bcc-like regions are located between the super-cubes in a way that Ga-atoms form a cubic primitive packing with V- and Cu-atoms in a part of the cubic voids. Vice versa represents V11Cu9Ga46 like V2Cu3Ga8 an ordered defect variant of CsCl, but with additional GaGa12-cuboctahedra. In total, V11Cu9Ga46 is an 8 × 8 × 8 superstructure of CsCl.
Co-reporter:Alexis Pediaditakis, Stefanie Haseloff, Harald Hillebrecht
Solid State Sciences 2011 Volume 13(Issue 8) pp:1465-1472
Publication Date(Web):August 2011
DOI:10.1016/j.solidstatesciences.2011.04.010
Two new boron-rich scandium borides were found with a structure closely related to tetragonal boron II (t-B192). Some black single crystals of ScB15 were obtained from a gallium melt besides rhombohedral ScB∼31. Its crystal structure (tP192; P41, a = 10.2995(15), c = 14.223(3) Å, 4603 refl., 438 param., R1(F) = 0.043, wR2(I) = 0.070) consists of a rod packing of B12-icosahedra and a new polyhedral B20+1 unit. Using a Cu-melt the main product is a ternary compound with the composition Sc2Cu1−xB45 (x ≈ 0.23) and a very similar crystal structure (tP192; P43, a = 10.2674(15), c = 14.261(3) Å, 5440 refl., 461 param., R1(F) = 0.032, wR2(I) = 0.080). In Sc2Cu1−xB45 one metal position is partially occupied by Cu, resulting in a different charge transfer by the metal atoms. This leads to slight differences in the B20+1 unit of the boron framework. Both single crystals were merohedrally twinned. The differences between ScB15 and Sc2Cu1−xB45 can be explained by the mnopq-rule of Jemmis.
Co-reporter:Dr. Natascha Vojteer;Dipl.-Chem. Vanessa Sagawe;Julia Stauffer;Dr. Melanie Schroeder;Dr. Harald Hillebrecht
Chemistry - A European Journal 2011 Volume 17( Issue 11) pp:3128-3135
Publication Date(Web):
DOI:10.1002/chem.201002968
Abstract
We present synthesis, crystal structure, hardness, and IR/Raman and UV/Vis spectra of a new compound with the mean composition LiB12PC. Transparent single crystals were synthesised from Ga, Li, B, red phosphorus and C at 1500 °C in boron nitride crucibles welded in Ta ampoules. Depending on the type of boron used for the synthesis we obtained colourless, brown and red single crystals with slightly different P/C ratios. Colourless LiB12PC crystallizes orthorhombic in the space group Imma (No. 74) with a=10.188(2) Å, b=5.7689(11) Å, c=8.127(2) Å and Z=4. Brown LiB12P0.89C1.11 is very similar, but with a lower P content. Red single crystals of LiB12P1.13C0.87 have a larger unit cell with a=10.4097(18) Å, b=5.9029(7) Å, c=8.2044(12) Å. EDX measurements confirm that the red crystals contain more phosphorus than the other ones. The crystal structure is characterized by a covalent network of B12 icosahedra connected by exohedral BB bonds and PP, PC or CC units. Li atoms are located in interstitials. The structure is closely related to MgB7, LiB13C2 and ScB13C. LiB12PC fulfils the electron counting rules of Wade and also Longuet-Higgins. Measurements of Vickers micro-hardness (HV=27 GPa) revealed that LiB12PC is a hard material. The optical band gaps obtained from UV/Vis spectra match the colours of the crystals. Furthermore we report on the IR and Raman spectra.
Co-reporter:Volker Adasch ; Melanie Schroeder ; Dominik Kotzott ; Thilo Ludwig ; Natascha Vojteer
Journal of the American Chemical Society 2010 Volume 132(Issue 39) pp:13723-13732
Publication Date(Web):September 14, 2010
DOI:10.1021/ja102659d
Single crystals of a new magnesium boride carbide MgxB50C8 (x = 2.4−4) were synthesized from the elements in a metallic melt using tantalum ampules. Crystals were characterized by single crystal X-ray diffraction and electron microprobe analysis. The variation of the Mg content results from different reaction conditions. The composition Mg∼3B50C8 is by far the most favored. It fulfills the electron counting rules of Wade and Longuet-Higgins and thus explains the light-green to yellow transparent color. The structure of Mg∼3B50C8 (C2/m, Z = 1, a = 8.9384(12) Å, b = 5.6514(9) Å, c = 9.6021(13) Å, β = 105.86(1)°) consists of B12 icosahedra. The icosahedra are interconnected by four exohedral B−B bonds to layers. The layers are connected to a three-dimensional covalent network by C2 and CBC units and further exohedral B−B bonds. The Mg sites are partially occupied. Different site occupation factors cause the various compositions and colors (Mg2.4B50C8, brown; Mg4B50C8, black). The vibrational spectra show the modes of B12 icosahedra and C2 and CBC units as well. Measurements of the microhardness according to Vickers and Knoop revealed remarkably high values of HV = 3286 (32.0 GPa) and HK = 3165 (31.5 GPa), which exceed the values of B4C. Optical spectra reveal a band gap of 2.7 eV for Mg∼3B50C8, in agreement to the observed color. This justifies an ionic description, and the formula can be written as (Mg2+)3(B122−)4(CBC+)2(C2)2.
Co-reporter:Alexis Pediaditakis, Melanie Schroeder, Vanessa Sagawe, Thilo Ludwig, and Harald Hillebrecht
Inorganic Chemistry 2010 Volume 49(Issue 23) pp:10882-10893
Publication Date(Web):November 2, 2010
DOI:10.1021/ic1012389
Single crystals of dark-red MgB7 were grown from the elements in a Cu-melt. The crystal structure (Pearson symbol oI64; space group Imma; a = 10.478(2) Å, b = 5.977(1) Å, c = 8.125(2) Å, 2842 reflns, 48 params, R1(F) = 0.018, R2(I) = 0.034) consists of a hexagonal-primitive packing of B12-icosahedra and B2-units in trigonal-prismatic voids. According to the UV−vis spectra and band structure calculations MgB7 is semiconducting with an optical gap of 1.9 eV. The long B−B distance of 2.278 Å within the B2-unit can be seen as a weak bonding interaction. The new Mg∼5B44 occurs beside the well-known MgB12 as a byproduct. Small fragments of the black crystals are dark-yellow and transparent. The crystal structure (Pearson symbol tP196, space group P41212, a = 10.380(2) Å, c = 14.391(3) Å, 4080 reflns, 251 params, R1(F) = 0.025, R2(I) = 0.037) is closely related to tetragonal boron-II (t-B192). It consists of B12-icosahedra and B19+1-units. With a charge of −6 for the B19+1-units and a Mg-content of ∼20 Mg-atoms per unit cell the observed Mg content in Mg∼5B44 is quite close to the expected value derived from simple electron counting rules. All compositions were confirmed by EDXS. The microhardness was measured on single crystals for MgB7 (HV = 2125, HK = 2004) and MgB12 (HV = 2360, HK = 2459).
Co-reporter:Melanie Schroeder, Tobias Schlöder, Anna J. Lehner and Harald Hillebrecht
Inorganic Chemistry 2010 Volume 49(Issue 7) pp:3130-3140
Publication Date(Web):February 26, 2010
DOI:10.1021/ic901784k
Single crystals of the new compounds Sc3Al3O5C2 and ScAl2ONC were obtained by reacting Sc2O3 and C in an Al-melt at 1550 °C. Their crystal structures continue the row of transition metal oxide carbides with an ordered distribution of anions and cations with ScAlOC as the first representative. In the structure of Sc3Al3O5C2 (P63/mmc, Z = 2, a = 3.2399(8) Å, c = 31.501(11) Å, 193 refl., 23 param., R1(F) = 0.024, wR2(I) = 0.058) the anions form a closest packing with five layers of oxygen separated by two layers of carbon atoms. Sc is placed in octahedral voids and Al in tetrahedral voids thus forming layers of AlOC3 tetrahedra and ScC6- and ScO6-octahedra, respectively. Surprisingly the layers of ScO6 octahedra are connected by an additional layer of undistorted trigonal bipyramids AlO5. The structure of ScAl2ONC (space group R3̅m, Z = 3, a = 3.2135(8) Å, c = 44.636(1) Å, 187 refl., 21 param., R1(F) = 0.023, wR2(F2) = 0.043) can directly be derived from the binary nitrides AlN (wurtzite-type) and ScN (rocksalt-type). The anions form a closest packing with alternating double layers of C and O separated by an additional layer of N. Again, Al and Sc occupy tetrahedral and octahedral voids, respectively. All compositions were confirmed by energy dispersive X-ray spectroscopy (EDXS) measurements on single crystals. According to band structure calculations Sc3Al3O5C2 is electron precise with a band gap of 0.3 eV. Calculations of charges and charge densities reveal that the mainly ionic bonding contains significant covalent contributions, too. As expected Sc and C show higher covalent shares than Al and O. The different coordinations of O, Al, and Sc are clearly represented in the corresponding p and d states.
Co-reporter:Dominik Kotzott, Harald Hillebrecht
Journal of Alloys and Compounds 2010 Volume 494(1–2) pp:88-93
Publication Date(Web):2 April 2010
DOI:10.1016/j.jallcom.2010.01.081
Single crystals of the new carbides W9Al3CoC3 were synthesized from a metallic melt and characterised by XRD and EDXS measurements. The crystal structure of W9Al3CoC3 was refined on the basis of single crystal data (hP32, P63/mmc, a = 7.9051(11) Å, c = 7.7869(16) Å, Z = 2, 304 reflections, 20 parameters, R1(F) = 0.0272, wR2(F2) = 0.0562). W9Al3CoC3 belongs to the family of κ-carbide M9M3′C3 or M10M3′C3 which are important components for cermets. Its crystal structure is characterised by CW6-octahedra which are connected to 6.3.6.3 Kagomé-net. Co and Al have no contacts to C-atoms. The metal atoms are ordered and all positions show full occupation. W9Al3CoC3 represents the first κ-carbide with a complete structure refinement on the basis of single crystal data. Micro-hardness measurement on single crystals yield values of HV = 15.5 GPa and HK = 12.5 GPa.
Co-reporter:Dominik Kotzott, Martin Ade, Harald Hillebrecht
Journal of Solid State Chemistry 2010 Volume 183(Issue 10) pp:2281-2289
Publication Date(Web):October 2010
DOI:10.1016/j.jssc.2010.07.048
Single crystals of the cubic τ-borides Ni23−xMxB6 (M=Zn, Ga, In, Sn, Ir) were synthesised from the elements at temperatures between 1200 and 1500 °C. The structure refinements show that the existence of boron-rich phases is quite common. Starting from the idealised composition Ni20M′3B6 a part of the metal atoms on site 8c is substituted by B4 tetrahedra. For M′=Ga a complete exchange seems to be possible leading to the composition Ni20GaB14. For M′=Zn and Sn the formation of solid solutions is less extended. For M′=In no exchange is observed but an unusual pattern of Ni/In distribution is observed. With M=Ir mixed occupations occur for all sites and the boron content varies, too. All compositions were confirmed by EDX measurements.Crystal structure of τ-Borides M23B6; M1: M8-cubes, M2: M12-cuboctahedra centred by M3, isolated M-atoms: M4; grey circles: boron, black circles: metal atoms.
Co-reporter:Martin Ade, Dominik Kotzott, Harald Hillebrecht
Journal of Solid State Chemistry 2010 Volume 183(Issue 8) pp:1790-1797
Publication Date(Web):August 2010
DOI:10.1016/j.jssc.2010.05.009
Single crystals of the new borides Ni12AlB8, and Ni10.6Ga0.4B6 were synthesized from the elements and characterized by XRD and EDXS measurements. The crystal structures were refined on the basis of single crystal data. Ni12AlB8 (oC252, Cmce, a=10.527(2), b=14.527(2), c=14.554(2) Å, Z=12, 1350 reflections, 127 parameters, R1(F)=0.0284, wR2(F2)=0.0590) represents a new structure type with isolated B atoms and B5 fragments of a B–B zig-zag chain. Because the pseudotetragonal metric crystals are usually twinned. Ni10.6Ga0.4B6 (oP68, Pnma, a=12.305(2), b=2.9488(6), c=16.914(3) Å, Z=4, 1386 reflections, 86 parameters, R1(F)=0.0394, wR2(F2)=0.104) is closely related to binary Ni borides. The structure contains B–B zig-zag chains and isolated B atoms. Ni12GaB8 is isotypical to the Al-compound (a=10.569(4), b=14.527(4) and c=14.557(5) Å).Graphical abstractPentameric B5-units are longest fragments of a B–B zig-zag chain ever characterized in a boride. They are found in the structures of Ni12AlB8 and Ni12GaB8. The compounds are formed on annealing boron-rich τ-borides like Ni20AlB14.
Co-reporter:Melanie Schroeder
Journal of the American Chemical Society 2009 Volume 131(Issue 34) pp:12172-12179
Publication Date(Web):August 5, 2009
DOI:10.1021/ja900206h
Single crystals of ScAlOC were obtained by reacting Sc2O3 and C in an Al melt at 1600 °C. The crystal structure (space group R3̅m, Z = 6, a = 3.2599(7) Å, c = 30.116(9) Å, 190 refl., 15 param., R1(F) = 0.0212, wR2(F2) = 0.0397) can directly be derived from the binary nitrides AlN and ScN. ScAlOC represents a new type of compound. It is the first oxide carbide of a transition metal with an ordered distribution of the anions. They form a cubic closest packing with alternating double layers of C and O while Al and Sc occupy tetrahedral and octahedral voids, respectively. The resulting polyhedra are AlC3O tetrahedra as well as ScO6 and ScC6 octahedra. According to band structure calculations ScAlOC is electron precise with an indirect band gap of 0.6 eV. Calculations of charges and charge densities reveal that the mainly ionic bonding contains significant covalent contributions, too. The black crystals of ScAlOC are very brittle and show a microhardness of 9.0 GPa. Thermal decomposition on air starts at 650 °C; in inert atmosphere ScAlOC is stable up to 1300 °C at least.
Co-reporter:Dominik Kotzott, Martin Ade, Harald Hillebrecht
Journal of Solid State Chemistry 2009 Volume 182(Issue 3) pp:538-546
Publication Date(Web):March 2009
DOI:10.1016/j.jssc.2008.10.036
Single crystals of the cubic τ-Borides Co23–xMxB6 (M=Al, Ga, Sn) were synthesised from the elements at temperatures between 1200 and 1500 °C. According to the structure refinements one (Ga, Sn: 8c) or two (Al: 4a and 8c) of the four independent metal sites show a mixed occupation Co/M resulting in the compositions Co20.9Al2.1B6, Co21.9Ga1.1B6, and Co21.4Sn1.6B6, respectively. Melts with Indium gave access to Co23B6 as the first binary τ-boride (Fm3¯m,a=10.4618(13) Å, 104 refl., 14 param., R1(F)=0.0132, wR2(F2)=0.0210). With M=Ir mixed occupations occur for all sites and the boron content varies. The composition for the boron-poor single crystal was Co16.2Ir6.8B6. A higher Ir-content enables the uptake of additional boron resulting in a composition Co12.3Ir8.9B10.5. This can be explained be the substitution of metal atoms on the 8c-site by B4-tetrahedra. A boron-rich phase was observed for the first time for a τ-boride of cobalt. All compositions were confirmed by EDX measurements.Single crystal investigations on τ-borides Co/M/B with M = Al, Ga, In, Sn, V, Ti, Ir explained the substitution processes. Furthermore the yielded the first binary boride, Co23B6, and a boron-rich Co12.3Ir8.9B10.5 containing B4-tetrahedra
Co-reporter:Johannes Etzkorn, Martin Ade, Dominik Kotzott, Monique Kleczek, Harald Hillebrecht
Journal of Solid State Chemistry 2009 Volume 182(Issue 5) pp:995-1002
Publication Date(Web):May 2009
DOI:10.1016/j.jssc.2009.01.003
Single crystals of Ga-containing MAX-phases Ti2GaC, Ti4GaC3, and Cr2GaC were grown from a metallic melt generated by an excess of Ga. This technique allows the crystal growth at different temperatures to control the product distribution. Compounds developed were Ti2GaC and TiC at 1500 °C, and Ti2GaC and Ti4GaC3 at 1300 °C. Crystal structures were refined from single crystal data. Ti2GaC and Cr2GaC were previously known, and belong to the Cr2AlC type as well as the solid solutions V2Ga1–xAlxC and Cr2Ga1–xAlxC. Ti4GaC3 is one of the few 413-phases (P63/mmc, a=3.0690(4) Å, c=23.440(5) Å) and the first Ga-containing representative. The crystal structures of MAX-phases are intergrowths of layers of an intermetallic MGa in a hexagonal stacking sequence with carbidic layers (MC)n of the NaCl type. The thickness of the layer depends from the value of n. The results of the structure refinements also demonstrate that also the structural details follow this description.Single crystals of Ga-containing MAX-Phases (TiC)n(TiGa) (n=1, 3) were grown from a metallic melt including and characterised by X-ray diffraction. Ti4GaC3 is one of the few 413-phase and the first containing Ga.
Co-reporter:Barbara Albert Dr. Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 46) pp:8640-8668
Publication Date(Web):
DOI:10.1002/anie.200903246
Abstract
Many of the fundamental questions regarding the solid-state chemistry of boron are still unsolved, more than 200 years after its discovery. Recently, theoretical work on the existence and stability of known and new modifications of the element combined with high-pressure and high-temperature experiments have revealed new aspects. A lot has also happened over the last few years in the field of reactions between boron and main group elements. Binary compounds such as B6O, MgB2, LiB1−x, Na3B20, and CaB6 have caused much excitement, but the electron-precise, colorless boride carbides Li2B12C2, LiB13C2, and MgB12C2 as well as the graphite analogue BeB2C2 also deserve special attention. Physical properties such as hardness, superconductivity, neutron scattering length, and thermoelectricity have also made boron-rich compounds attractive to materials research and for applications. The greatest challenges to boron chemistry, however, are still the synthesis of monophasic products in macroscopic quantities and in the form of single crystals, the unequivocal identification and determination of crystal structures, and a thorough understanding of their electronic situation. Linked polyhedra are the dominating structural elements of the boron-rich compounds of the main group elements. In many cases, their structures can be derived from those that have been assigned to modifications of the element. Again, even these require a critical revision and discussion.
Co-reporter:Johannes Etzkorn, Harald Hillebrecht
Journal of Solid State Chemistry 2008 Volume 181(Issue 6) pp:1342-1346
Publication Date(Web):June 2008
DOI:10.1016/j.jssc.2008.02.037
Single crystals of the new carbide Ta3Al2CoC were synthesised from metallic melt and characterized by XRD, EDX and WDX measurements. The crystal structure of Ta3Al2CoC was refined on the basis of single crystal data (cF112, Fd3¯m, a=11.6153(13) Å, Z=16, 169 reflections, 13 parameters, R1(F)=0.0315, wR2(F2)=0.0857). Ta3Al2CoC belongs to the great family of η-carbides M3M3′C or M4M2′C which are important components for cermets. Its crystal structure is characterised by TaC6-octahedra, which are connected to a three-dimensional net. Co and Al have icosahedral surroundings without contacts to C-atoms. All positions show full occupation. Ta3Al2CoC represents the first η-carbide with a complete structure refinement on the basis of single crystal data.Single crystals of the η-carbide Ta3Al2CoC were grown from a Co-melt. Although η-carbides are technologically very important as a constituent of cermets this is the first report on a single crystal study. The structure analysis of this quarternary variant shows the close similarity to the Ni2Ti-structure as an ordering and filling variant. All sites are completely occupied and well ordered.
Co-reporter:Dominik Kotzott, Martin Ade, Harald Hillebrecht
Solid State Sciences 2008 Volume 10(Issue 3) pp:291-302
Publication Date(Web):March 2008
DOI:10.1016/j.solidstatesciences.2007.09.014
Single crystals of two forms of Cr2IrB2, the τ-boride Cr7.9Ir14.1B6 and orthorhombic Cr2B were synthesised from the elements at temperatures between 1450 and 1650 °C. α-Cr2IrB2 was obtained at 1650 °C and crystallizes in the Mo2IrB2 crystal structure type (oP20, Pnnm, Z = 4, a = 9.210(1) Å, b = 7.112(1) Å, c = 2.9833(5) Å, 493 refl., 27 param. R1(F) = 0.0220, wR2(F2) = 0.0521) containing 4-membered B4 chain fragments with the terminating B atoms in trans position. β-Cr2IrB2 (1450 °C) forms a low temperature form in a new crystal structure type (oC40, Cmcm, Z = 8, a = 3.0024(7) Å, b = 9.945(2) Å, c = 13.236(2) Å, 424 refl., 28 param., R1(F) = 0.0279, wR2(I) = 0.0532) containing B4 chain fragments of trigonal prisms BM6 with the terminating B atoms in cis position. These B4 units were observed for the first time. A structure refinement with single crystal data was done for the τ-boride Cr7.9Ir14.1B6 (Fm3¯m, a = 11.2024(19) Å, 151 refl., 17 param., R1(F) = 0.0275, wR2(F2) = 0.0297). Refinement of single crystal data shows that orthorhombic Cr2B (oF48, Fddd, Z = 16, a = 4.275(2) Å, b = 7.452(3) Å, c = 14.795(5) Å, 214 refl., 17 param., R1(F) = 0.0251, wR2(F2) = 0.0625) belongs to the CuMg2 type and not to the Mn4B type with partial boron occupation. The compositions were confirmed by EDX and WDX measurements.
Co-reporter:Natascha Vojteer Dipl.-Chem.;Melanie Schroeder Dipl.-Chem.;Caroline Röhr Dr. Dr.
Chemistry - A European Journal 2008 Volume 14( Issue 24) pp:7331-7342
Publication Date(Web):
DOI:10.1002/chem.200701949
Abstract
We present the synthesis, crystal structure, hardness, IR/Raman and UV/Vis spectra, and FP-LAPW calculations of the electronic structure of Li2B12Si2, the first ternary compound in the system Li/B/Si. Yellow, transparent single crystals were synthesized from the elements in tin as solvent at 1500 °C in h-BN crucibles in arc-welded Ta ampoules. Li2B12Si2 crystallizes orthorhombic in the space group Cmce (no. 64) with a=6.1060(6), b=10.9794(14), c=8.4050(8) Å, and Z=4. The crystal structure is characterized by a covalent network of B12 icosahedra connected by Si atoms and Li atoms located in interstitial spaces. The structure is closely related to that of MgB12Si2 and fulfils the electron-counting rules of Wade and Longuet-Higgins. Measurements of Vickers (HV=20.3 GPa) and Knoop microhardness (HK=20.4 GPa) revealed that Li2B12Si2 is a hard material. The band gap was determined experimentally and calculated by theoretical means. UV/Vis spectra revealed a band gap of 2.27 eV, with which the calculated value of 2.1 eV agrees well. The IR and Raman spectra show the expected oscillations of icosahedral networks. Theoretical investigations of bonding in this structure were carried out with the FP-LAPW method. The results confirm the applicability of simple electron-counting rules and enable some structural specialties to be explained in more detail.
Co-reporter:Verena Kuntze, Rainer Lux, Harald Hillebrecht
Journal of Solid State Chemistry 2007 Volume 180(Issue 1) pp:198-206
Publication Date(Web):January 2007
DOI:10.1016/j.jssc.2006.10.009
Co-reporter:Volker Adasch Dr.;Kai-Uwe Hess Dr.;Thilo Ludwig Dr.;Natascha Vojteer Dipl.-Chem. Dr.
Chemistry - A European Journal 2007 Volume 13(Issue 12) pp:
Publication Date(Web):19 JAN 2007
DOI:10.1002/chem.200601002
Single crystals of two modifications of the new magnesium boride carbide MgB12C2 were synthesized from the elements in a metallic melt by using tantalum ampoules. Crystals were characterized by single-crystal X-ray diffraction and electron microprobe analysis (energy-dispersive (EDX) and wavelength-dispersive (WDX) X-ray spectroscopy). Orthorhombic MgB12C2 is formed in a Cu/Mg melt at 1873 K. The crystal structure of o-MgB12C2 (Imma, Z=4, a=5.6133(10), b=9.828(2), c=7.9329(15) Å, 574 reflections, 42 variables, R1(F)=0.0208, wR2(I)=0.0540) consists of a hexagonal primitive array of B12 icosahedra with Mg atoms and C2 units in trigonal-prismatic voids. Each icosahedron has six exohedral BB and six BC bonds. Carbon is tetrahedrally coordinated by three boron atoms and one carbon atom with a remarkably long CC distance of 1.727 Å. Monoclinic MgB12C2 is formed in an Al/Mg melt at 1573 K. The structure of m-MgB12C2 (C2/c, Z=4, a=7.2736(11), b=8.7768(13), c=7.2817(11) Å, β=105.33(3)°, 1585 reflections, 71 variables, R1(F)=0.0228, wR2(I)=0.0610) may be described as a distorted cubic close arrangement of B12 icosahedra. Tetrahedral voids are filled by C atoms and octahedral voids are occupied by Mg atoms. The icosahedra are interconnected by four exohedral BB bonds to linear chains and by eight interstitial C atoms to form a three-dimensional covalent network. Both compounds fulfill the electron-counting rules of Wade and Longuet-Higgins.
Co-reporter:Volker Adasch, Kai-Uwe Hess, Thilo Ludwig, Natascha Vojteer, Harald Hillebrecht
Journal of Solid State Chemistry 2006 Volume 179(Issue 7) pp:2150-2157
Publication Date(Web):July 2006
DOI:10.1016/j.jssc.2006.04.021
Single crystals of Mg2B24C, a new boron-rich boridecarbide of magnesium, were synthesized as black needles and columns by reaction of the elements in Ta ampoules and BN crucibles at 1300 °C. The crystal structure was determined by X-ray diffraction (P-4n 2, a=8.9391(13)Åa=8.9391(13)Å, c=5.0745(10)Åc=5.0745(10)Å, Z=2Z=2, 713 reflections, 64 variables, R1(F)=0.0235R1(F)=0.0235, wR2(I)=0.0591wR2(I)=0.0591). It is closely related to “tetragonal boron I” and can be described as a tetragonal rod packing of corner-linked B12 icosahedra with C and Mg atoms in the voids. Each B12 icosahedron has 2 B–C bonds and 10 exohedral bonds to other icosahedra, 2 within the rod and 4×2 to neighbouring rods. The isolated C atoms are 4-fold coordinated forming distorted tetrahedra. Mg is placed on two crystallographically independent positions within the three-dimensional B12C network. Mg2B24C is the first example for a compound related to “tetragonal boron I” with a stoichiometric composition.Mg2B24C, a new boron-rich boridecarbide of magnesium, was synthesized from the elements. Its crystal structure is closely related to “tetragonal boron I” and can be described as a tetragonal rod packing of corner-linked B12 icosahedra with C and Mg atoms in the voids. Mg2B24C is the first example for a compound related to “tetragonal boron I” with a stoichiometric composition.
Co-reporter:Thilo Ludwig, Harald Hillebrecht
Journal of Solid State Chemistry 2006 Volume 179(Issue 6) pp:1623-1629
Publication Date(Web):June 2006
DOI:10.1016/j.jssc.2006.02.013
We report on the synthesis of MgB12Si2 the first ternary compound in the system B/Mg/Si. Yellow transparent single crystals were yielded from the elements at 1600 °C in h-BN crucibles welded in Ta ampoules. MgB12Si2 crystallizes orthorhombic in the space group Pnma with a=10.9797(11)Å, b=6.1098(7)Å, c=8.3646(12)Å and Z=4Z=4. The crystal structure is characterized by layers of B12 icosahedra, connected by isolated Si atoms to a three-dimensional framework. Mg atoms are placed in voids of the framework. Each icosahedron forms 8 B–Si bonds and 4 exohedral B–B bonds. The Si atoms are tetrahedrally coordinated by B atoms of the B12 icosahedra.The crystal structure of MgB12Si2, the first ternary compound of the system Mg/B/Si, is characterized by layers of B12 icosahedra, connected by isolated Si atoms to a three dimensional framework. Mg atoms are placed in voids of the framework.
Co-reporter:Volker Adasch, Kai-Uwe Hess, Thilo Ludwig, Natascha Vojteer, Harald Hillebrecht
Journal of Solid State Chemistry 2006 Volume 179(Issue 9) pp:2916-2926
Publication Date(Web):September 2006
DOI:10.1016/j.jssc.2006.03.045
Single crystals of MgB12 were synthesized from the elements in a Mg/Cu melt at 1600 °C. MgB12 crystallizes orthorhombic in space group Pnma with a=16.632(3)Å, b=17.803(4)Å and c=10.396(2)Å. The crystal structure (Z=30Z=30, 5796 reflections, 510 variables, R1(F)=0.049R1(F)=0.049, wR2(I)=0.134wR2(I)=0.134) consists of a three dimensional net of B12 icosahedra and B21 units in a ratio 2:1. The B21 units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB12.35 or Mg0.97B12 , respectively. This is in good agreement with the value of MgB11.25 as expected by electronic reasons to stabilize the boron polyhedra B122- and B214-.The new crystal structure of MgB12 is characterized by a Kagome net of B12 icosahedra and B21 units, which are observed for the first time. The Mg atoms are placed in voids of the framework.
Co-reporter:Volker Adasch, Kai-Uwe Hess, Thilo Ludwig, Natascha Vojteer, Harald Hillebrecht
Journal of Solid State Chemistry 2006 Volume 179(Issue 9) pp:2900-2907
Publication Date(Web):September 2006
DOI:10.1016/j.jssc.2006.03.009
For the first time, single crystals of Mg containing β-rhombohedral boron MgB17.4 were synthesised from the elements in a Mg/Cu melt at 1600 °C. The crystal structure determined by the refinement of single crystal data (space group R-3m , a=10.991(2)Å, c=24.161(4)Å, 890 reflections, 123 variables, R1(F)=0.049R1(F)=0.049, wR2(I)=0.122wR2(I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to β-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB17.4 and Mg5.85B101.9, respectively, confirmed by WDX measurements. The single crystals of MgB17.4 show the highest Mg content ever found. Preliminary measurements indicate no superconductivity.Unit cell of MgB17.4 (rhombohedral setting).
Co-reporter:Natascha Vojteer Dipl.-Chem. Dr.
Angewandte Chemie 2006 Volume 118(Issue 1) pp:
Publication Date(Web):22 NOV 2005
DOI:10.1002/ange.200502325
Wade hat Recht: Li2B12C2 (siehe Kristallstruktur) und LiB13C2, die ersten borreichen Boridcarbide des Lithiums, sind (fast) farblos und stöchiometrisch zusammengesetzt. B12-Ikosaeder und C2- bzw. CBC-Einheiten bilden ein dreidimensionales Gerüst mit eingelagerten Li-Kationen, und die Ladungsverteilung lässt sich gemäß den Wade-Regeln als (Li+)2B122−C2 bzw. (Li+)B122−(CBC+) beschreiben. Die Proben wurden durch Hochtemperatursynthese in Metallschmelzen erzeugt.
Co-reporter:Natascha Vojteer,Harald Hillebrecht
Angewandte Chemie International Edition 2006 45(1) pp:165-168
Publication Date(Web):
DOI:10.1002/anie.200502325
Co-reporter:A.C. Wagner, A. Cröll, H. Hillebrecht
Journal of Crystal Growth (15 August 2016) Volume 448() pp:109-116
Publication Date(Web):15 August 2016
DOI:10.1016/j.jcrysgro.2016.05.024
•Spark Plasma Sintering SPS can be used for the synthesis of SiGe.•Samples synthesized by SPS can be combined to feed rods for single crystal growth.•Si–Ge distribution is described by Pfann's equation.•Zone levelling results in homogenous single crystals.•Doped samples show the expected thermoelectric properties.The availability of suitable feed rods for Si–Ge bulk crystal growth is known to be a limiting factor in floating zone growth and other growth techniques. In this work, three Si-rich SiGe single crystals were crystallized by an optical floating zone technique in a double ellipsoid mirror furnace. The feed rods were prepared by pre-synthesis in the Spark Plasma Sintering (SPS) process starting with powders of different compositions. In a detailed section the preparation method of consolidation by mechanical alloyed powders to feed rods will be given. Results from two growth experiments starting with uniform compositions with 11 at% and 20 at% germanium as well as a zone leveling experiment with a segmented feed rod consisting of a starting zone with 32 at% Ge will be discussed. The latter experiment resulted in a crystal with nearly no axial segregation.
