Preparation, crystal structure and properties of RuIn3

Journal of

ALLOYS AND COMPOUNDS ELSEVIER

Journal of Alloysand Compounds226 (1995) 59--64

Preparation, crystal structure and properties of Ruin3 Rainer P6ttgen Max-Planck-lnstitutfiir FestkOrperforschung,Heisenbergstrasse 1, D-70569Stuttgart, Germany Received9 January 1995

Abstract The title compound was prepared from the elemental components in a tantalum tube at 950 °C. The crystal structure of Ruin3 was refined from single-crystal X-ray data: P42/mnm (no. 136), a = 700.3( 1) pm, c = 724.7(2) pm, V= 0.3554(2) nm3, Z= 4, wR2 = 0.0512 for 372 F 2 values and 16 variables. Ruin3 is isotypic with FeGa3. The structure of Ruin3 is compared with the related structures of U3Si2, Zr3A12and Na3Hg2. Susceptibility and electrical resistivity measurements indicate weak Pauli paramagnetism and poor metallic conductivity, respectively. Keywords: Synthesis;Crystalstr~cture;Magneticsusceptibility;Electricalresistivity

1. Introduction Several years ago, Holleck et al. [ 1 ] reported on the prep° aration of Ruin 3. They concluded from X-ray powder patterns that Ruin3 is isotypic with CoGa3 [2]. The crystal structure of Ruin 3 was recently refined from X-ray powder data by Roof et al. [3]. They also assumed isotopism with CoGa3 and described the structure in the non-centrosymmetric space group P4n2. However, a study of the atomic coordinates shows that the deviations from centrosymmetricity are very small indeed. During phase investigations of rare-earth metal-goldtin(indium) systems [4,5], several new compounds REzAu2Sn(In ) ( R E = Y , Gd-Tm, Lu) were discovered. They crystallize in the space group P4/mbm (U3Si 2 type [6,7] or P4z/mnm/ZrsAlz type [8]) with structures very similar to that reported for Ruin3. The redetermination of the structure of Ruin 3 is reported in the present paper, motivated by the slructural relationship to the other stannides and indides.

Table 1 Tetragonallatticeconstantsof Ruin3 (standarddeviationsin parentheses) a (pm)

c (pm)

c/a

v (nm3)

Ref.

699.3 699.83(3) 700.3( 1)

724.0 724.40(4) 724.7(2)

1.035 1.035 1.035

0.3541 0.35478(5) 0.3554(2)

[ 1] [3] This work

at 500 °C, annealed at 950 °C for ten days and then quenched in air. The reaction resulted in a fine-grained light-grey powder which could easily be isolated from the tantalum tube. Only some parts of the sample were agglomerated. Ruin3 is stable in air, and single crystals exhibit metallic lustre. The samples were characterized by Guinier powder diagrams using Cu Ka~ radiation with silicon (a = 543.07 pm) as an internal standard. To assure correct indexing, the observed patterns were compared with the calculated ones [ 10] taking the atomic positions as obtained from the structure refinement. The tetragonal lattice constants (Table 1) were obtained by least-squares fits of the powder data. They compare well with the data published earlier (Table 1).

2. Sample preparation and lattice constants Starting materials for the preparation of Ruin3 were ruthenium powder (Degussa, 200 mesh, > 99.9%) and indium teardrops (Johnson Matthey, > 99.9%). The elementalcomponents were mixed in the ideal atomic ratio and sealed in a tantalum tube under an argon pressure of about 800 mbar. The argon was purified previously by molecular sieves, titanium sponge at 900 K and an oxisorb catalyst [9]. The tantalum tube was sealed in a quartz ampoule, heated for 2 h 0925-8388/95/$09.50 © 1995ElsevierScienceS.A. All fightsreserved SSD10925-8388(95)01575-2

3. Physical properties The magnetic susceptibilities of polycrystalline Ruin3 pieces were measured from 4.2 to 300 K with a MPMS SQUID magnetometer (Quantum Design, Inc.) at magnetic flux densities up to 5.5 T. Over the whole temperature range investigated, Ruin3 shows negative susceptibility values (Fig. 1). The slight upturn in the X vs. Tplot below about 50

R. POttgen/ Journal of Alloys and Compounds 226 (1995) 59-64

60

-90

i, m l m

-94

o

E E

-98 0000

0 E P<

•

•

•

•

•

•

-102

-106

-110 0

I

I

I

I

I

50

100

150

200

250

300

T[K] Fig. 1. Temperature dependence of the magnetic susceptibility of Ruin3, measured at 1 T.

4000

3000

E 0

C

2000

CL

1000

I

I

I

I

I

50

100

150

200

250

300

T [K] Fig. 2. Temperature dependence of the electrical resistivity of Ruln3.

K may be attributed to a very small amount of paramagnetic impurities. The susceptibilities were not dependent on the external magnetic field. Between 50 K and room temperature the susceptibility is essentially temperature independent with a value of - 9 9 ( 1 ) × 10 - 6 e m u mo1-1. For an approximate diamagnetic correction we assume susceptibilities of 43.2× 10 -6 emu mo1-1 and - 6 4 × 10 - 6 e m u mol -~ for ruthenium and indium, respectively [ 11 ]. With these values we obtain a susceptibility of - 1 4 8 . 8 × 10 -6 emu mo1-1,

somewhat larger than the experimental value. Thus, the Pauli paramagnetism of Ruin3 is quite weak and of the same order of magnitude as the intrinsic diamagnetism. Resistivity measurements (Fig. 2) were performed on small platelets (typical dimensions 0.7 ×0.8 × 1.0 mm 3) with a conventional four-point set-up. The cooling and heating curves measured at a constant current between 4.2 and 300 K were essentially identical and reproducible for several samples. The specific resistivity of Ruin3 decreases with

R. Piittgen / Journal of Alloys and Compounds 226 (1995) 59-64 Table 2 Crystal data and structure refinement for Ruin3 Empirical formula Formula weight Temperature Wavelengths Crystal system Space group Unit cell damensions Formula units per cell Calculated density Crystal s i ~ Absorption correction Transmission ratio (max:min) Absorption coefficient F(O00) Orange for data collection Range in h/c/ Scan mode Total no. reflections Independent reflections Refinement method Data/restraints / parameters Goodness-of-fit on F 2 Final R indices [1> 2o-(1) ] R indices (all data) Extinction ~oefficient Largest diff. peak and hole

Ruin3 445.53 g mol 293(2) K 56.087 pm tetragonal

61

4 K. However, their sample was obtained from an indium flux which contained cerium as well as ruthenium. 1

4. Structure refinement

P42/mnm see Table 1 Z= 4 8.326 Mg m -3 20 × 25 × 5 0 / ~ m - 3 from psi-scan data 1:0.960 12.189 m m - 1 764 3.19 to 24.88 ° -3~
Table 3 Atomic coordinates and isotropic displacement parameters (pm 2) for Ruin3 Atom

P42/mnm

x

y

z

U~q

Ru Inl In2

L~f z~c gj

0.34510(8) 0 0.15547(4)

x 1/2 x

0 0 0.26224(6)

40(2) 102(1) 88(1)

U~q is defined as one third of the trace of the orthogonalized U~j tensor.

decreasing temperature as is typical for metallic conductors. At room temperature the specific resistivity has a value of about 38130/z~cm, considerably higher than the room temperature values of 7.6/zD, cm and 8.37/~f~cm for ruthenium and indium, respectively [ 11 ]. The residual resistance ratio between 1300K and 4.2 K is about 45, in contrast to the data of Roof et al. [ 3 ]. These authors also reported metallic behaviour, but with a resistance ratio of 2.8 between 290 K and

The single crystal used for the structure determination was isolated from the fine-grained powder of the annealed sample. Buerger diffraction patterns showed a primitive tetragonal cell with the Laue symmetry 4/mmm. The systematic extinctions (Okl only observed with k+l=2n, hO0 only with h ---2n) led to the space groups P42/mnm, P4n2 and P42nm of which the centrosymmetric group P4z/mnm (no. 136) was found to be correct during the structure refinements. Intensity data were collected on a four-circle diffractometer (CAD4) with graphite monochromatized Ag Ka radiation and a scintillation counter with pulse height discrimination. Experimental details are listed in Table 2. The starting atomic parameters were taken from the previous investigation of Xue-San and Ching-Kwei on FeGa3 [ 12]. The structure was then successfully refined in the centrosymmetric group P42/mnm using SHELXL-93 [ 13] with anisotropic displacement parameters for all atoms. The final residuals are listed in Table 2. A subsequent difference Fourier synthesis gave no indication for the occupancy of additional atomic sites. Atomic coordinates and interatomic distances are given in Tables 3 and 4. Further details on the structure refinement are available Attempts to refine the structure in the non-centrosymmetric subgroup P4n2 (no. 118), chosen in Refs. [ 1] and [ 3 ], did not improve the results and we conclude that the structure is centrosymmetric, in agreement with the results on FeGa3 [ 12] and CoGa3 [ 14]. The gallides and indides with the same composition, i.e. RuGa3, RhGa3, OsGa3, IrGa3 [15], aReGa3 [ 16], Coin 3 [ 17-19], Rhln 3 and IrIn3 [ 15], reported to be isotopic with CoGa3 [2] probably also crystallize in space group P4z/mnm. Contact Fachinformationszentrum Karlsruhe, Gesellschaft far wissenschaftlich-technische Information mbH, 76344 Eggenstein-Leopoldshafen, Germany, quoting the depository number CSD-58759, the name of the author and the journal citation.

Table 4 Interatomic distances (pm) in the structure of Ruin3. All distances shorter than 520 pm (Ru-Ru) and 440 p m (Ru-In, In-In) are listed. Standard deviations are all equal or less than 0.1 pm Ru:

2 2 4 1

In 1 In2 In2 Ru

264.9 267.2 277.4 306.8

In 1:

2 4 4 2

Ru In2 In2 Inl

264.9 315.8 325.9 362.4

In2:

1 2 1 2 2 1 4 1

Ru Ru In2 Inl Inl In2 In2 In2

267.2 277.4 308.0 315.8 325.9 344.6 374.8 380.1

62

R. POttgen/ Journal of Alloys and Compounds 226 (1995) 59--64

5. Discussion

Ruin3 belongs to a large series of compounds which are built up from CsC1- or W-like cubes and AIB2-1ike trigonal prisms as shown in Fig. 3. The W-like slab in Ruin3 is built up by the In2 atoms. The Inl atom which centres this distorted cube has four In2 neighbours at 315.8 pm and four In2 at 325.9 pm. Two faces of this distorted In2 cube are capped by ruthenium atoms at a distance of 264.9 pm (In2-Ru). Additionally, the Inl atom has two further Inl neighbours along the z axis at the much larger In-In distance of 362.4 pm. The average In-In distance for the ten nearest In neighbours of Inl equals 329.2 pm. The eight-fold somewhat cube-like coordination of Inl by eight In2 is very similar to the coordination in elemental indium (tetragonal body-centred structure) [20]. There, each indium atom has eight neighbours at 337.6 pm and four neighbours at 324.8 pm with an average In-In distance of 333.3 pm. Similar In-In bond lengths were also observed in the In-In zig-zag chains of Ca4In2N (316.2 pm) and Sr4In2N (332.0 pm) [21]. The distorted trigonal prisms of the AIB2-1ike slab are formed by the In2 atoms. One half of these prisms is centred by ruthenium atoms in an ordered manner. Only every second AIB2 slab is occupied alternately. Each ruthenium atom has a trigonal prismatic indium coordination. Two square faces

U3Si2 z = 0 112 u • Si •

3

(~

of the trigonal prism are capped by further indium atoms; the third one is capped by a ruthenium atom. The R u i n distances range from 264.9 pm to 277.4 pm with an average value of 271.7 pm. These R u i n bonds are quite strong. The average distance of 271.7 pm is significantly shorter than the sum of the metallic radii for coordination number 12 of 300.2 pm, taking the data from Teatum et al. [22]. The Ru-Ru distances of 306.8 pm within the A1B2 slab may only be considered as very weak interactions. In elemental ruthenium (Mg type) the Ru-Ru bond lengths are 265 pm [20] ; twice the metallic radius for CN 12 of ruthenium amounts to 267.8 pm [22]. The Ru-Ru distances in the related compounds RuSn2 (CuAI2 type) [23] and RuGa (CsCI type) [ 24] are 285 pm and 301 pm, respectively. Thus, Ru-Ru bonding in Ruin3 does only play a subordinate role compared with R u i n and In-In bonding. The In2 atoms form the trigonal prisms of the AIB2 slab. Their coordination is somewhat irregular, when compared with the coordination of Ru and Inl. Each In2 atom has three ruthenium neighbours; one at 267.2 pm and two more at 277.4 pm. The average In2-Ru bond length of 274.0 pm is 9.1 pm longer than the Inl-Ru bond, but still strongly bonding. Additionally, the In2 atoms have 11 indium neighbours which cover the relatively wide range from 308.0 pm to 380.1 pm. The average In2-In distance amounts to 346.8 pm and is somewhat longer than the average In-In distance of 333.3

Ruin3 z = 0 1/2 Ru o • In O C) In

Q + 0.24 G + 0.26

z = 0112 Na O • Na C ) ( ~ Hg o + 0 . 1 9 • _+0.31

Fig. 3. Projectionsof the crystalstructuresof U3Si2 (P4/mbm), Ruin3 (P42/mnm), Zr3A12 (P42/mnm) and Na3Hg2(P42/mnm)onto the xy planes.For the title compound,the Inl atomsare all withinthe distortedcubes;the In2 atomsbuiltthe AIB2-1iketrigonalprisms.

R. POttgen / Journal of Alloys and Compounds 226 (1995) 59-64

pm in elemental indium [20]. However, the five nearest indium neighbours of In2 have smaller In-In distances than in elemental indium. Such a large range of In-In distances is also observed in several alkaline indium compounds with indium clusters, such as K17In41 (295.6-379.1 pm), NalTGa29In12 (302.0-302.7 pm) [25], NaTInlL76 (285.8347.3 pm) [26], Kalnll (296.6-328.7 pm) and Rb8InH (296.6-328.8 pm) [27]. As already mentioned above, Ruin3 may be described as built up from distorted W-like [ In 1In28] cubes and [Ruin26] trigonal prisms. These slabs are outlined in a projection of the crystal structure of Ruin3 in the upper right-hand part of Fig. 3. Three other binary structure types of intermetallics, namely U3Si2 [6,7], Zr3A12 [8] and NaaHg2 [28] show similar structural features. They are shown together with Ruln3 in Fig. 3. The most symmetric, the basic structure of this series is the U3Si2 type [6,7], which consists of quite regular [SiU6] trigonal prisms and [UUs] square prisms. U3Si2 has the smallest unit cell of these compounds with parallel USi2 and U layers on the mirror planes at z---0 and z = 1/2, respectively. The aluminide Zr3A12 [8] has a superstructure of the U3Si2 type. The differences in size between the Zr and A1 atoms, when compared with U and Si result in small distortions of both prism types. This leads to a doubling of the lattice constant c and a shift of the A1 atoms away from the mirror plane. NaaHg2 [28] has the same space group and composition as Zr3A12, but a slightly different atomic arrangement. This structure type consists of [HgNa6] trigonal prisms but it has no centred square prisms. There, all sodium atoms are on the same heights, only at z = 0 and z = 1/2, respectively. Instead of centred cubes, Na3Hg2 contains centred [ NaNa4] squares. As in Zr3A12,the mercury atoms in Na3Hg2 are also shifted away from the mirror planes. Ruin3 has the same space group and similar building elements as ZraAI2 and Na3Hg2, but a different composition. Only half of the trigonal prisms are occupied and the distortions of the prisms are different. While the Zr and Na atoms in Zr3Al 2 and Na3Hg2 are shifted on the mirror planes along the xy diagonal, the In atoms in Ruin3 are shifted along z. The atoms centring the trigonal prisms show the inverse behaviour. While the AI2 and Hg2 pairs in Zr3A12 and Na3Hg2 shift along the z axis, the Ru atoms in Ruin3 remain on the mirror planes at z = 0 and z = 1/2, respectively, and shift in the xy diagonal. The different distortions in these structure types have a large influence on chemical bonding within the trigonal prisms. In the structure of U3Si2, the silicon atoms form pairs with a bond distance of 240.3 pm [7], close to the Si-Si bond length of 235 pm in elemental silicon [20]. The A1 atoms in Zr3A12 also form pairs with an AI-AI distance of 270 pm. Since these AI2 pairs are shifted in z, they are in contact with a second AI2 pair only 294 pm apart. In cubic close-packed aluminium each A1 atom has 12 AI neighbours at 286.3 pm [ 29,30]. In Na3Hg2, two Hg2 pairs with a Hg-Hg distance of 301 pm always form Hg4 units, with a distance of 296 pm

63

between the pairs along z. Both of these bond distances are smaller than twice the metallic radius of mercury of 314.6 pm [22]. In contrast to these three structure types, the ruthenium atoms in Ruin3 have only very weak interactions to each other; they do not form pairs. Owing to the shift of the In2 atoms from z = 1/4 to +0.24 and +0.26, the AIB2 slab slightly contracts at the middle square plane and slightly opens at both ends. The ruthenium atoms therefore deviate and move away from the centre of the prisms towards the corners (see Fig. 3), avoiding the formation of Ru2 pairs.

Acknowledgments I thank Prof. Dr. A. Simon for his interest and steady support of this work. I am also grateful to Dr. H. Borrmann and H. G~rttling for the help with the single-crystal data collection, Dr. R.K. Kremer for helpful discussions on the physical properties, W. R6thenbach for the Guinier powder patterns, E. Brticher for the susceptibility measurement, N. Weishaupt for the electrical conductivity measurement and Dr. W. Gerhartz (Degussa AG) for a generous gift of ruthenium powder. The Stiftung Stipendienfonds des Verbandes der Chemischen Industrie supported my research by a Liebig stipend.

References [ 1] H. Holleck, H. Nowotny and F. Benesovsky, Monatsh. Chem., 95 (1964) 1386. [2] K. Schubert, H.L. Lukas, H.-G. MeiBner and S. Bahn, Z. Metallkd., 50 (1959) 534. [3] R.B. Roof, Z. Fisk and J.L. Smith, Powder Diffraction, 1 (1986) 20. [4] R. P0ttgen, Z. Naturforsch., 49b (1994) 1309. [5] R. P0ttgen, Z. Naturforsch., 49b (1994) 1525. [6] W.H. Zachariasen, Acta Crystallogr., 1 (1948) 265. [7] K. Remschnig, T. LeBihan, H. Noel and P. Rogl, J. SolidState Chem., 97 (1992) 391. [8] C.G. Wilson and F.J. Spooner, Acta Crystallogr., 13 (1960) 358. [9] H.L. Krauss and H. Stach, Z. Anorg. Allg. Chem., 366 (1969) 34. [ 10] K. Yvon, W. Jeitschko and E. Parth~, J. Appl. Crystallogr., 10 (1977) 73. [11] R.C. Weast (ed.), Handbook of Chemistry and Physics, 66th edn., CRC Press, Boca Raton, FL, 1985. [ 12] Chen Xue-San and Lalng Ching-Kwei, Chinese J. Phys., 21 (1965) 849. [13] G.M. Sheldrick, SHELXL-93, Program for the crystal structure refinement, University of G6ttingen, Germany, 1993. [14] Chang Tao-Fan and Lalng Ching-Kwei, Chinese J. Phys., 22 (1966) 952. [ 15] K. Schubert, H. Breimer, R. Gohle, H.L Lukas, H.-G. MeiBner and E. Stolz, Naturwissenschaften, 45 (1958) 360. [ 16] S.V. Popova and L.N. Fomieheva, Inorg. Mater., 18 (1982) 205. [ 17] H.H. Stadelmaier, J.D. Sch6bel, R.A. Jones and C.A. Shumaker, Acta Crystallogr., B29 (1973) 2926. [18] M.V. Katrich, N.N. Matynshenko and Yu.G. Titov, Soy. Phys. Crystallogr, 22 (1977) 107. [ 19 ] M. Ellner and S. Bhan, J. Less- Common Met., 79 ( 1981 ) P1. [20] J. Donohue, The Structures of the Elements, Wiley, New York, 1974. [21] G. Cordier and S. R6nninger, Z. Naturforsch., 42b (1987) 825.

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[22] E. Teatum, K. Gschneidner Jr. and J. Waber, Rep. LA-2345, US Department of Commerce, Washington, DC, 1960. [23] O. Schwomma, H. Nowotny and A. Wittmann, Monatsh. Chem., 95 (1964) 1538. [24] W. Jeitschko, H. Holleck, H. Nowotny and F. Benesovsky, Monatsh. Chem., 94 (1963) 838. [25] G. Cordier and V. Mtiller, Z. Naturforsch., 49b (1994) 721.

[26] S.C. Sevov and J.D. Corbett, Inorg. Chem., 31 (1992) 1895. [27] W. Blase, G. Cordier, V. Mailer, U. H~iuBermann, R. Nesper and M. Somer, Z. Namrforsch., 48b (1993) 754. [28] J.W. Nielsen and N.C. Baenziger, Acta Crystallogr., 7 (1954) 277. [ 29 ] H.M. Otte, W.G. Montagne and D.O. Welch, J. Appl. Phys., 34 (1963) 3149. [30] W. Witt, Z. Naturforsch., 22a (1967) 92.