On the electrochemically grown quasi-one-dimensional KCu{sub 7{minus}x}S{sub 4} series (0 {le} x {le} 0.34): Nonstoichiometry superlattice, and unusual phase transitions
- Clemson Univ., SC (United States)
- Okayama Univ. of Science (Japan)
Whiskers of the quasi-one-dimensional copper(I) sulfide series were grown by employing electrochemical (E-Chem) methods via anodic dissolution of copper electrodes. The compound series can be prepared at 110 C in ethylenediamine solution of polysulfide K{sub 2}S{sub n} (n = 5,6) electrolytes and, in some cases, CuCl. Single-crystal structure analysis has reconfirmed the once ambiguous space group issue, and the study has also revealed that the KCu{sub 7}S{sub 4} phase reported by Ohtani et al. is nonstoichiometric. The present investigations on as-grown whiskers show that the previously observed unusual insulator-to-metal transition can be reproduced by the KCu{sub 6.86}S{sub 4} phase. Refined cell volumes increase linearly with increasing copper content. The extended framework resembles the (NH{sub 4})Cu{sub 7}S{sub 4} structure. It consists of quasi-one-dimensional Cu{sub 4}S{sub 4} columns interlinked by tetrahedral copper chains. New evidence shows that the title series exhibits complicated structure patterns with regard to the ordering of the Cu{sup +} cation along the tetrahedral chain. The nonstoichiometry and cation ordering are likely responsible for the anomalies observed in transport properties. A self-consistent model with respect to local ordering is discussed, and a recently proposed diffusive one-dimensional ordering model at the transitions is reiterated. The detailed synthesis and structure, along with preliminary electron diffraction studies and temperature-dependent magnetic susceptibility measurements, of the title series are presented.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 675634
- Journal Information:
- Chemistry of Materials, Vol. 10, Issue 10; Other Information: PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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