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DOI: 10.1039/A903945G (Paper) Reference Section for: J. Mater. Chem., 1999, 9, 2293-2296

Cu0.66EuTe2, KCu2EuTe4 and Na0.2Ag2.8EuTe4: compounds with modulated square Te nets

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Rhonda Patschke, Paul Brazis, Carl R. Kannewurf and Mercouri G. Kanatzidis

Abstract

Reactions of europium with copper or silver in molten alkali metal/polytelluride fluxes have produced the new polytelluride compounds, Cu0.66EuTe2, KCu2EuTe4 and Na0.2Ag2.8EuTe4. All three compounds are stable in air and crystallize as red–brown plates in tetragonal space groups. Cu0.66EuTe2 crystallizes in the space groupP4/nmm with a = 4.481(2), c = 10.260(3) Å (at 23[thin space (1/6-em)]°C) and Z = 2. KCu2EuTe4 and Na0.2Ag2.8EuTe4 are isostructural and crystallize in the space group P4mm with a = 4.4365(6), c = 11.365(2) Å (at 23[thin space (1/6-em)]°C) for KCu2EuTe4, and a = 4.4544(6), c = 11.106(2) Å (at 23[thin space (1/6-em)]°C) for Na0.2Ag2.8EuTe4. Cu0.66EuTe2 adopts the CaMnBi2 structure-type with square antiprismatic europium atoms sandwiched between an anti-PbO type layer of [CuTe]– and a flat square net of tellurium. The structure of KCu2EuTe4 can be derived from that of Cu0.66EuTe2 by systematically replacing half of the europium atoms in the framework with potassium. Electron diffraction studies on KCu2EuTe4 and Na0.2Ag2.8EuTe4 suggest a 1a × 7b superlattice, the result of a charge density wave (CDW) distortion in the square Te net of these compounds. KCu2EuTe4 exhibits semimetallic behavior while Na0.2Ag2.8EuTe4 is a p-type semiconductor with a bandgap of 0.24 eV.

References

  1. R. Patschke, J. Heising, J. Schindler, C. R. Kannewurf and M. G. Kanatzidis, J. Solid State Chem., 1998, 135, 111 CrossRef CAS.
  2. R. Patschke, J. Heising, P. Brazis, C. R. Kannewurf and M. G. Kanatzidis, Chem. Mater., 1998, 10, 695 CrossRef CAS.
  3. R. Patschke, P. Brazis, C. R. Kannewurf and M. G. Kanatzidis, J. Mater. Chem., 1998, 8, 2587 RSC.
  4. R. Patschke, P. Brazis, C. R. Kannewurf and M. G. Kanatzidis, Inorg. Chem., 1998, 37, 6562 CrossRef CAS.
  5. R. Patschke, P. Brazis, C. R. Kannewurf and M. G. Kanatzidis, manuscript in preparation.
  6. F.-Q. Huang, W. Choe, S. Lee and J. Chu, Chem. Mater., 1998, 10, 1320 CrossRef CAS.
  7. J. A. Cody and J. A. Ibers, Inorg. Chem., 1995, 34, 3165 CrossRef CAS.
  8. M. A. Pell and J. A. Ibers, Chem. Ber./Recueil, 1997, 130, 1 CrossRef CAS.
  9. A. A. Narducci and J. A. Ibers, Chem. Mater., 1998, 10, 2811 CrossRef CAS.
  10. B. K. Norling and H. Steinfink, Inorg. Chem., 1966, 5, 1488 CrossRef CAS.
  11. V. W. Kroönert and K. Z. Plieth, Z. Anorg. Allg. Chem., 1965, 336, 207 CrossRef.
  12. (a) N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, Pergamon Press, New York, 1984, p. 1434 Search PubMed; (b) M. Guittard and J. Flahaut, Synthesis of Lanthanide and Actinide Compounds, Kluwer Academic Publishers, Netherlands, 1991, p. 321 Search PubMed.
  13. W. Bensch and P. Dürichen, Chem. Ber., 1996, 129, 1489 CAS.
  14. Cu0.66EuTe2 was synthesized from a mixture of 0.298 g Rb2Te (1.0 mmol) 0.032 g Cu (0.5 mmol), 0.038 g Eu (0.25 mmol) and 0.510 g Te (4.0 mmol) which was sealed under high vacuum in a 13 mm quartz ampoule. The ampoule was heated to 400 °C for 12 h, kept at that temperature for 12 h, heated to 850 °C in 24 h, and kept at that temperature for 6 days. The tube was then cooled to 400 °Cat –4 °C h–1, and then quenched to room temperature in 4 h. The excess Rb2Tex flux was removed, under a nitrogen atmosphere, with dimethyl formamide and small red–brown square plates were extracted from the melt. The crystals are air and water stable. Microprobe analysis carried out on the single crystal used for X-ray data collection gave an average composition of Cu0.66Eu1.0Te2.0.
  15. KCu2EuTe4 was synthesized from a mixture of 0.165 g K2Te (0.8 mmol), 0.025 g Cu (0.4 mmol), 0.061 g Eu (0.4 mmol) and 0.306 g Te (2.8 mmol). The heating profile and isolation method used was the same as described above.14 Microprobe analysis carried out on randomly selected crystals gave an average composition of K0.8Cu1.9Eu1.0Te3.4.
  16. Na0.2Ag2.8EuTe4 was synthesized from a mixture of 0.208 g Na2Te (1.2 mmol), 0.097 g Ag (0.9 mmol), 0.046 g Eu (0.3 mmol) and 0.612 g Te (4.8 mmol). The heating profile and isolation method used were the same as described above.14 Thin square red–brown plate crystals (67% yield based on Ag) gave an average composition by microprobe analysis of Na0.51Ag1.11Eu1.0Te3.21.
  17. G. Cordier, H. Schäfer and P. Woll, Z. Naturforsch., Teil B, 1985, 40, 1097 Search PubMed.
  18. R. Patschke, J. Heising, P. Brazis, C. R. Kannewurf and M. G. Kanatzidis, Chem. Mater., 1998, 10, 695 CrossRef CAS.
  19. (a) G.-H. Gweon, J. D. Denlinger, J. A. Clack, J. W. Allen, C. G. Olson, E. DiMasi, M. C. Aronson, B. Foran and S. Lee, Phys. Rev. Lett., 1998, 81, 886 CrossRef CAS; (b) E. DiMasi, B. Foran, M. C. Aronson and S. Lee, Phys Rev. B, 1996, 54, 13587 CrossRef CAS; (c) E. DiMasi, M. C. Aronson, J. F. Mansfield, B. Foran and S. Lee, Phys. Rev. B, 1995, 52, 14516 CrossRef CAS; (d) B. Foran and S. Lee, J. Am. Chem. Soc., 1994, 116, 154 CrossRef CAS; (e) E. DiMasi, B. Foran, M. C. Aronson and S. Lee, Chem. Mater., 1994, 6, 1867 CrossRef CAS; (f) B. Foran, M. C. Aronson, S. Lee and M. C. Anderson, Chem. Mater., 1993, 5, 974 CrossRef CAS.
  20. X. Zhang, J. Li, B. Foran, S. Lee, H.-Y. Guo, T. Hogan, C. R. Kannewurf and M. G. Kanatzidis, J. Am. Chem. Soc., 1995, 117, 10513 CrossRef CAS.
  21. J. Hanko, M. G. Kanatzidis, M. Evain, O. Gourdon and F. Boucher, submitted for publication.
  22. N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, Pergamon Press, New York, 1984, p. 1443 Search PubMed.
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