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Crystal structure of the quaternary compound CuTa2InTe4 from X-ray powder diffraction
ARTICLE IN PRESS Physica B 403 (2008) 3228– 3230
Contents lists available at ScienceDirect
Physica B journal homepage: www.elsevier.com/locate/physb
Crystal structure of the quaternary compound CuTa2InTe4 from X-ray powder diffraction ˜ oz b, S. Duran b, M. Quintero b G.E. Delgado a,, A.J. Mora a, P. Grima-Gallardo b, M. Mun a b
Laboratorio de Cristalografı´a, Departamento de Quı´mica, Facultad de Ciencias, Universidad de Los Andes, Me´rida 5101, Venezuela ´rida 5101, Venezuela Centro de Estudios de Semiconductores, Departamento de Fı´sica, Facultad de Ciencias, Universidad de Los Andes, Me
a r t i c l e in f o
a b s t r a c t
Article history: Received 17 October 2007 Received in revised form 30 March 2008 Accepted 8 April 2008
The crystal structure of the new quaternary compound CuTa2InTe4 was studied using X-ray powder diffraction data. The powder pattern refined by the Rietveld method indicates that this material crystallizes in the tetragonal system with space group I-4¯2m (No. 121), Z ¼ 2, and unit cell parameters a ¼ 6.1963(2) A˚, c ¼ 12.4164(4) A˚, c/a ¼ 2.00 and V ¼ 476.72(3) A˚3. The structural and instrumental refinement of 28 parameters led to Rp ¼ 10.4%, Rwp ¼ 11.1%, Rexp ¼ 6.8% and w2 ¼ 2.7 for 96 independent reflections. & 2008 Elsevier B.V. All rights reserved.
PACS: 61.10.Nz 61.50.Nw 61.66.Fn Keywords: Semiconductors Crystal structure X-ray diffraction
1. Introduction Alloys with composition (I–III–VI2)1x(II–VI)x can be produced by the addition of a II–VI binary to chalcopyrite I–III–VI2 structures. In this system it is possible to find the compositions I–II–III–VI3, I2–II–III2–VI5, and I–II2–III–VI4 for x ¼ 1/2, 1/3 and 2/3, respectively. All these phases fulfill the rules of formation of adamantane compounds [1] and belong to the normal semiconductor compound families of the third-, fourthand fifth-order derivatives of the II–VI binary semiconductors, respectively [2]. In previous works, the preparation and characterization of some members of the I–II2–III–VI4 family were reported. Particularly, the compounds CuFe2InSe4 [3–5], CuV2InSe4 [6] and CuCo2InSe4 [7] showed a tetragonal structure close to the parent chalcopyrite structure. More recently, the crystal structure of CuFe2InSe4 was refined by the Rietveld method, indicating that this material crystallizes in the tetragonal stannite structure, space group I4¯2m [5], and constituted the first compound of the I–II2–III–VI4 family that crystallizes in a sphalerite derivative structure. In contrast, all the phases reported of the type AgCd2GaS4 [8], AgCd2GaSe4 [9] and the related systems Corresponding author. Tel.: +58 274 2401372; fax: +58 274 2401286.
E-mail address: [email protected] (G.E. Delgado). 0921-4526/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2008.04.022
Ag1–xCuxCd2GaS4 [10], AgCd2Ga1–xInxS4 [10] and AgCd2–xMnxGaS4 [11], crystallizes in the orthorhombic space group Pmn21 with structures related to the wurtzite. Concerning the new system (CuInTe2)1x(TaTe)x, the ternary CuInTe2 (x ¼ 0) crystallizes in the chalcopyrite I4¯2d structure with unit cell parameters a ¼ 6.194 A˚ and c ¼ 12.415 A˚ [12], whereas for the binary TaTe (x ¼ 1) there is no report. Recently, a high solubility of Ta in the chalcopyrite structure of the system (CuInTe2)1x(TaSe)x has been shown, where the quaternary compound CuTaInSe3 (x ¼ 0.5) crystallizes with unit cell parameters very close to the parent CuInSe2 [13]. In this work we report the crystal structure analysis of the new quaternary compound CuTa2InTe4, using X-ray powder diffraction data, which crystallize with a structure related to the sphalerite. 2. Experimental The sample of CuTa2InTe4 was synthesized using the melt and annealing technique [14]. Stoichiometric quantities of high pure Cu, Ta, In and Te elements were charged in an evacuated quartz ampoule, which was previously subject to pyrolisis in order to avoid reaction of the starting materials with quartz. Then, the ampoule was sealed under vacuum and the fusion process was carried out inside a furnace (vertical position) heated up to
ARTICLE IN PRESS G.E. Delgado et al. / Physica B 403 (2008) 3228–3230
1500 1C at a rate of 20 1C/h, with a stop of 48 h at 450 1C (melting temperature of Te). The ampoule was shaken using a mechanical system throughout the heating process in order to guarantee the complete mixing of all the elements, especially Ta, which has a very high melting point (2996 1C). Then, the temperature was gradually cooled at the same rate down to 600 1C. The ampoule was kept at this temperature for a period of 30 days. Finally, the sample was cooled to room temperature at a rate of 10 1C/h. The stoichiometric relation of the sample was investigated by the SEM technique, using a Hitachi S2500 microscope equipped with a Kedex EDX accessory. Five different regions of the ingot were scanned and the average atomic percentages are: Cu (13.4%), Ta (23.2%), In (12.4%) and Te (51.0%), which are in good agreement with the ideal composition 1:2:1:4. For the X-ray analysis, a small quantity of the sample was ground mechanically in an agate mortar and pestle. The resulting fine powder was mounted on a zero-background holder covered with a thin layer of petroleum jelly. The X-ray powder diffraction data were collected at 298(1) K, in the y/2y reflection mode using a Siemens D5005 diffractometer equipped with an X-ray tube (CuKa radiation: l ¼ 1.5418 A˚; 30 kV and 15 mA) and a diffracted beam graphite monochromator. The specimen was scanned from 101 to 1001 2y, with a step size of 0.021 and a counting time of 60 s. Quartz was used as an external standard.
3229
cell. A detailed pattern examination taking in account the sample composition, cell parameters and lattice type suggested that this material is isomorphic with CuFe2InSe4 [5]; the first compound of the I–II2–III–VI4 semiconductor family that crystallizes in a sphalerite derivative structure, which crystallize in the tetragonal space group I4¯2m. The Rietveld refinement [16] of the whole diffraction pattern was carried out using the FULLPROF program [17–18]. The atomic
3. Results and discussion Fig. 1 shows the resulting X-ray powder diffractogram for the CuTa2InTe4 compound. Some peaks with very low intensities cannot be indexed, which could be some impurities or oxides. The first 20 peaks position of the main phase were indexed using the program DICVOL04 [15], which gave a unique solution in a tetragonal cell with a ¼ 6.193(1) A˚ and c ¼ 12.400(2) A˚. The systematic absences study (h k l: h+k+l ¼ 2n) indicated an I-type
Fig. 2. Unit cell diagram of CuTa2InTe4.
Fig. 1. Final plot of the Rietveld refinement, showing the observed, calculated and difference patterns of CuTa2InTe4. Vertical markers refer to the calculated positions of the Bragg reflections. Un indexed peaks are denoted by asterisks (*).
ARTICLE IN PRESS 3230
G.E. Delgado et al. / Physica B 403 (2008) 3228–3230
Table 1 Unit cell, atomic coordinates, isotropic temperature factor and selected geometric parameters (A˚, 1) for CuTa2InTe4 Atom
Ox.
Wyck.
x
y
z
Foc
Cu Ta In Te
+1 +2 +3 2
2b 4d 2a 4a
0 0 0 0.263(2)
0 1/2 0 0.263(2)
1/2 1/4 0 0.124(1)
1 1 1 1
2.59(1)
Ta–Te
2.69(1)
In–Te
Cu–Tea b
c
Te –Cu–Te Tea–Cu–Tec
110.8(4) 106.9(4)
x4 x2
d
Te–Ta–Te Te–Ta–Tee
109.0(4) 109.7(4)
x4 x2
B (A˚2) 0.6(5) 0.6(5) 0.6(5) 0.6(5) 2.77(1) f
Te–In–Te Teg–In–Te
108.0(4) 2 112.5(4) 2
Symmetry codes. a 0.5x, 0.5y, 0.5+z. b 0.5y, 0.5+x, 0.5z. c 0.5+x, 0.5+y, 0.5+z. d 0.5y, 0.5+x, 0.5z. e x, 1y, z. f y, x, z. g x, y, z.
coordinates of the compound CuFe2InSe4 [5] were used as the initial model for the refinement of CuTa2InTe4. The angular dependence of the peak full-width at half-maximum (FWHM) was described by Caglioti’s formula [19]. Peak shapes were described by the pseudo-Voigt profile function. The background variation was described by a polynomial with six coefficients. The thermal motion of the atoms was described by one overall isotropic temperature factor. The final figures of merit for 28 instrumental and structural variables were as follows: 10.4%, Rwp ¼ 11.1%, Rexp ¼ 6.8% and w2 ¼ 2.7 for 4501 step intensities and 96 independent reflections. The final Rietveld plot is shown in Fig. 1. Fig. 2 shows the unit cell diagram of CuTa2InTe4. Unit cell parameters, atomic coordinates, isotropic temperature factor, selected bond distances and angles are shown in Table 1. CuTa2InTe4 is a normal adamantine-structure compound and can be described as a derivative of the sphalerite structure [1]. The tetrahedrons containing the In atoms [mean TeyTe distance 4.53(2) A˚] are greater than those containing the Ta atoms [means TeyTe distance 4.40(2) A˚] and Cu atoms [mean TeyTe distance 4.22(2) A˚], respectively. The interatomic distances are shorter than the sum of the respective ionic radii for tetrahedrally bonded structures [20]. The Cu–Te, 2.59(1) A˚ bond distances are in good agreement with those found in related compounds such as CuInTe2 (2.59 A˚) [12], CuGaTe2 (2.62 A˚) [21], Cu3TaTe4 (2.60 A˚) [22], Cu2ZnGeTe4 (2.575 A˚) [23] and Cu2SnTe3 (2.63 A˚ average) [24]. The Ta–Te distance, 2.69(1) A˚, compare well with those observed in Cu3TaTe4 (2.65 A˚) [22] and Cu2GeTe3 (2.62 A˚ average) [25]. The In–Te, 2.77(1) A˚, bond distances are also close to similar bonds found in the compounds CuInTe2 (2.79 A˚) [12] and AgIn5Te8 (2.76 A˚ average) [26].
4. Conclusions The structure of the new quaternary semiconductor CuTa2InTe4 was refined by the Rietveld method from X-ray powder diffraction data. This material crystallizes in the tetragonal space group I4¯2m, with a derivative sphalerite structure.
Acknowledgments This work was supported by CDCHT-ULA (Grants C-1446-0705-ED, C-1447-07-05-ED and C-961-99-05-A) and FONACIT (Grant LAB-97000821). References [1] E. Parthe´, in: J.H. Westbrook, R.L. Fleischer (Eds.), Intermetallic Compounds, Principles and Applications, vol. 1, Wiley, Chichester, UK, 1995 (Chapter 14.). [2] J.M. Delgado, Inst. Phys. Conf. Ser. 152 (1998) 147. [3] P. Grima-Gallardo, K. Cardenas, M. Quintero, J. Ruiz, G.E. Delgado, Mater. Res. Bull. 36 (2001) 861. [4] P. Grima-Gallardo, K. Cardenas, L. Molina, M. Quintero, J. Ruiz, G.E. Delgado, Phys. Stat. Sol. (a) 187 (2001) 395. [5] G.E. Delgado, A.J. Mora, P. Grima-Gallardo, M. Quintero, J. Alloys Compds. 454 (2008) 306. ˜ oz, G. Delgado, J.M. Bricen ˜ o, [6] P. Grima-Gallardo, S. Duran, M. Quintero, M. Mun H. Romero, J. Ruiz, Phys. Stat. Sol. (a) 193 (2002) 217. ˜ oz, J. Ruiz, C. Power, J. Gonzalez, Y. Legodec, [7] P. Grima-Gallardo, M. Mun ˜ o, J.M. Bricen ˜ o, Phys. Stat. Sol. (b) 241 (2004) 1795. P. Munsch, J.P. Itie, V. Bricen [8] S.I. Chykhrij, O.V. Parasyuk, V.O. Halka, J. Alloys Compds. 312 (2000) 189. [9] I.D. Olekseyuk, L.D. Gulay, O.V. Parasyuk, O. Husak, E.M. Kadykalo, J. Alloys Compds. 343 (2002) 125. [10] I.D. Olekseyuk, O.V. Parasyuk, O. Husak, L.V. Piskach, S.V. Volkov, V.I. Pekhnyo, J. Alloys Compds. 402 (2005) 186. [11] G.Ye. Davydyuk, V.P. Sachanyuk, S.V. Voronyuk, I.D. Olekseyuk, Y.E. Romanyuk, O.V. Parasyuk, Physica B 373 (2006) 355. [12] K.S. Knight, Mater. Res. Bull. 27 (1992) 161. ˜ oz, S. Dura´n, G.E. Delgado, M. Quintero, J. Ruiz, Mat. [13] P. Grima-Gallardo, M. Mun Res. Bull. 42 (2007) 2067. ˜ oz, S. Dura´n, M. Quintero, E. Quintero, [14] P. Grima-Gallardo, M. Mun M. Morocoima, E. Caldero´n, G.E. Delgado, H. Romero, Phys. Stat. Sol. (a), accepted. [15] A. Boultif, D. Loue¨r, J. Appl. Crystallogr. 37 (2004) 724. [16] H.M. Rietveld, J. Appl. Crystallogr. 2 (1969) 65. [17] J. Rodriguez-Carvajal, Fullprof (version 4.0, 2007), Laboratoire Le´on Brillouin (CEA-CNRS), France. [18] T. Roisnel, J. Rodriguez-Carvajal, Mater. Sci. Forum 378–381 (2001) 118. [19] G. Cagliotti, A. Paoletti, F.P. Ricci, Nucl. Instrum. 3 (1958) 223. [20] S.D. Shannon, Acta Crystallogr. A 32 (1976) 751. [21] M. Leo´n, J.M. Merino, J.L. de Vidales, J. Mater. Sci. 27 (1992) 4495. [22] J. Li, H.-Y. Guo, D.M. Proserpio, A. Sironi, J. Solid State Chem. 117 (1995) 247. [23] O.V. Parasyuk, I.D. Olekseyuk, L.V. Piskach, J. Alloys Compds. 397 (2005) 169. [24] G.E. Delgado, A.J. Mora, G. Marcano, C. Rinco´n, Cryst. Res. Technol. 43 (2008) 433. [25] G.E. Delgado, A.J. Mora, M. Pirela, A. Vela´zquez, M. Villarroel, B.J. Ferna´ndez, Phys. Stat. Sol. (a) 201 (2004) 2900. [26] A.J. Mora, G.E. Delgado, C. Pineda, T. Tinoco, Phys. Stat. Sol. (a) 201 (2004) 1477.
Contents lists available at ScienceDirect
Physica B journal homepage: www.elsevier.com/locate/physb
Crystal structure of the quaternary compound CuTa2InTe4 from X-ray powder diffraction ˜ oz b, S. Duran b, M. Quintero b G.E. Delgado a,, A.J. Mora a, P. Grima-Gallardo b, M. Mun a b
Laboratorio de Cristalografı´a, Departamento de Quı´mica, Facultad de Ciencias, Universidad de Los Andes, Me´rida 5101, Venezuela ´rida 5101, Venezuela Centro de Estudios de Semiconductores, Departamento de Fı´sica, Facultad de Ciencias, Universidad de Los Andes, Me
a r t i c l e in f o
a b s t r a c t
Article history: Received 17 October 2007 Received in revised form 30 March 2008 Accepted 8 April 2008
The crystal structure of the new quaternary compound CuTa2InTe4 was studied using X-ray powder diffraction data. The powder pattern refined by the Rietveld method indicates that this material crystallizes in the tetragonal system with space group I-4¯2m (No. 121), Z ¼ 2, and unit cell parameters a ¼ 6.1963(2) A˚, c ¼ 12.4164(4) A˚, c/a ¼ 2.00 and V ¼ 476.72(3) A˚3. The structural and instrumental refinement of 28 parameters led to Rp ¼ 10.4%, Rwp ¼ 11.1%, Rexp ¼ 6.8% and w2 ¼ 2.7 for 96 independent reflections. & 2008 Elsevier B.V. All rights reserved.
PACS: 61.10.Nz 61.50.Nw 61.66.Fn Keywords: Semiconductors Crystal structure X-ray diffraction
1. Introduction Alloys with composition (I–III–VI2)1x(II–VI)x can be produced by the addition of a II–VI binary to chalcopyrite I–III–VI2 structures. In this system it is possible to find the compositions I–II–III–VI3, I2–II–III2–VI5, and I–II2–III–VI4 for x ¼ 1/2, 1/3 and 2/3, respectively. All these phases fulfill the rules of formation of adamantane compounds [1] and belong to the normal semiconductor compound families of the third-, fourthand fifth-order derivatives of the II–VI binary semiconductors, respectively [2]. In previous works, the preparation and characterization of some members of the I–II2–III–VI4 family were reported. Particularly, the compounds CuFe2InSe4 [3–5], CuV2InSe4 [6] and CuCo2InSe4 [7] showed a tetragonal structure close to the parent chalcopyrite structure. More recently, the crystal structure of CuFe2InSe4 was refined by the Rietveld method, indicating that this material crystallizes in the tetragonal stannite structure, space group I4¯2m [5], and constituted the first compound of the I–II2–III–VI4 family that crystallizes in a sphalerite derivative structure. In contrast, all the phases reported of the type AgCd2GaS4 [8], AgCd2GaSe4 [9] and the related systems Corresponding author. Tel.: +58 274 2401372; fax: +58 274 2401286.
E-mail address: [email protected] (G.E. Delgado). 0921-4526/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2008.04.022
Ag1–xCuxCd2GaS4 [10], AgCd2Ga1–xInxS4 [10] and AgCd2–xMnxGaS4 [11], crystallizes in the orthorhombic space group Pmn21 with structures related to the wurtzite. Concerning the new system (CuInTe2)1x(TaTe)x, the ternary CuInTe2 (x ¼ 0) crystallizes in the chalcopyrite I4¯2d structure with unit cell parameters a ¼ 6.194 A˚ and c ¼ 12.415 A˚ [12], whereas for the binary TaTe (x ¼ 1) there is no report. Recently, a high solubility of Ta in the chalcopyrite structure of the system (CuInTe2)1x(TaSe)x has been shown, where the quaternary compound CuTaInSe3 (x ¼ 0.5) crystallizes with unit cell parameters very close to the parent CuInSe2 [13]. In this work we report the crystal structure analysis of the new quaternary compound CuTa2InTe4, using X-ray powder diffraction data, which crystallize with a structure related to the sphalerite. 2. Experimental The sample of CuTa2InTe4 was synthesized using the melt and annealing technique [14]. Stoichiometric quantities of high pure Cu, Ta, In and Te elements were charged in an evacuated quartz ampoule, which was previously subject to pyrolisis in order to avoid reaction of the starting materials with quartz. Then, the ampoule was sealed under vacuum and the fusion process was carried out inside a furnace (vertical position) heated up to
ARTICLE IN PRESS G.E. Delgado et al. / Physica B 403 (2008) 3228–3230
1500 1C at a rate of 20 1C/h, with a stop of 48 h at 450 1C (melting temperature of Te). The ampoule was shaken using a mechanical system throughout the heating process in order to guarantee the complete mixing of all the elements, especially Ta, which has a very high melting point (2996 1C). Then, the temperature was gradually cooled at the same rate down to 600 1C. The ampoule was kept at this temperature for a period of 30 days. Finally, the sample was cooled to room temperature at a rate of 10 1C/h. The stoichiometric relation of the sample was investigated by the SEM technique, using a Hitachi S2500 microscope equipped with a Kedex EDX accessory. Five different regions of the ingot were scanned and the average atomic percentages are: Cu (13.4%), Ta (23.2%), In (12.4%) and Te (51.0%), which are in good agreement with the ideal composition 1:2:1:4. For the X-ray analysis, a small quantity of the sample was ground mechanically in an agate mortar and pestle. The resulting fine powder was mounted on a zero-background holder covered with a thin layer of petroleum jelly. The X-ray powder diffraction data were collected at 298(1) K, in the y/2y reflection mode using a Siemens D5005 diffractometer equipped with an X-ray tube (CuKa radiation: l ¼ 1.5418 A˚; 30 kV and 15 mA) and a diffracted beam graphite monochromator. The specimen was scanned from 101 to 1001 2y, with a step size of 0.021 and a counting time of 60 s. Quartz was used as an external standard.
3229
cell. A detailed pattern examination taking in account the sample composition, cell parameters and lattice type suggested that this material is isomorphic with CuFe2InSe4 [5]; the first compound of the I–II2–III–VI4 semiconductor family that crystallizes in a sphalerite derivative structure, which crystallize in the tetragonal space group I4¯2m. The Rietveld refinement [16] of the whole diffraction pattern was carried out using the FULLPROF program [17–18]. The atomic
3. Results and discussion Fig. 1 shows the resulting X-ray powder diffractogram for the CuTa2InTe4 compound. Some peaks with very low intensities cannot be indexed, which could be some impurities or oxides. The first 20 peaks position of the main phase were indexed using the program DICVOL04 [15], which gave a unique solution in a tetragonal cell with a ¼ 6.193(1) A˚ and c ¼ 12.400(2) A˚. The systematic absences study (h k l: h+k+l ¼ 2n) indicated an I-type
Fig. 2. Unit cell diagram of CuTa2InTe4.
Fig. 1. Final plot of the Rietveld refinement, showing the observed, calculated and difference patterns of CuTa2InTe4. Vertical markers refer to the calculated positions of the Bragg reflections. Un indexed peaks are denoted by asterisks (*).
ARTICLE IN PRESS 3230
G.E. Delgado et al. / Physica B 403 (2008) 3228–3230
Table 1 Unit cell, atomic coordinates, isotropic temperature factor and selected geometric parameters (A˚, 1) for CuTa2InTe4 Atom
Ox.
Wyck.
x
y
z
Foc
Cu Ta In Te
+1 +2 +3 2
2b 4d 2a 4a
0 0 0 0.263(2)
0 1/2 0 0.263(2)
1/2 1/4 0 0.124(1)
1 1 1 1
2.59(1)
Ta–Te
2.69(1)
In–Te
Cu–Tea b
c
Te –Cu–Te Tea–Cu–Tec
110.8(4) 106.9(4)
x4 x2
d
Te–Ta–Te Te–Ta–Tee
109.0(4) 109.7(4)
x4 x2
B (A˚2) 0.6(5) 0.6(5) 0.6(5) 0.6(5) 2.77(1) f
Te–In–Te Teg–In–Te
108.0(4) 2 112.5(4) 2
Symmetry codes. a 0.5x, 0.5y, 0.5+z. b 0.5y, 0.5+x, 0.5z. c 0.5+x, 0.5+y, 0.5+z. d 0.5y, 0.5+x, 0.5z. e x, 1y, z. f y, x, z. g x, y, z.
coordinates of the compound CuFe2InSe4 [5] were used as the initial model for the refinement of CuTa2InTe4. The angular dependence of the peak full-width at half-maximum (FWHM) was described by Caglioti’s formula [19]. Peak shapes were described by the pseudo-Voigt profile function. The background variation was described by a polynomial with six coefficients. The thermal motion of the atoms was described by one overall isotropic temperature factor. The final figures of merit for 28 instrumental and structural variables were as follows: 10.4%, Rwp ¼ 11.1%, Rexp ¼ 6.8% and w2 ¼ 2.7 for 4501 step intensities and 96 independent reflections. The final Rietveld plot is shown in Fig. 1. Fig. 2 shows the unit cell diagram of CuTa2InTe4. Unit cell parameters, atomic coordinates, isotropic temperature factor, selected bond distances and angles are shown in Table 1. CuTa2InTe4 is a normal adamantine-structure compound and can be described as a derivative of the sphalerite structure [1]. The tetrahedrons containing the In atoms [mean TeyTe distance 4.53(2) A˚] are greater than those containing the Ta atoms [means TeyTe distance 4.40(2) A˚] and Cu atoms [mean TeyTe distance 4.22(2) A˚], respectively. The interatomic distances are shorter than the sum of the respective ionic radii for tetrahedrally bonded structures [20]. The Cu–Te, 2.59(1) A˚ bond distances are in good agreement with those found in related compounds such as CuInTe2 (2.59 A˚) [12], CuGaTe2 (2.62 A˚) [21], Cu3TaTe4 (2.60 A˚) [22], Cu2ZnGeTe4 (2.575 A˚) [23] and Cu2SnTe3 (2.63 A˚ average) [24]. The Ta–Te distance, 2.69(1) A˚, compare well with those observed in Cu3TaTe4 (2.65 A˚) [22] and Cu2GeTe3 (2.62 A˚ average) [25]. The In–Te, 2.77(1) A˚, bond distances are also close to similar bonds found in the compounds CuInTe2 (2.79 A˚) [12] and AgIn5Te8 (2.76 A˚ average) [26].
4. Conclusions The structure of the new quaternary semiconductor CuTa2InTe4 was refined by the Rietveld method from X-ray powder diffraction data. This material crystallizes in the tetragonal space group I4¯2m, with a derivative sphalerite structure.
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