Electrical Properties of the Square-Antiprismatic Chain Compounds M4Br4Os (M = Y, Er) and M4Te4Z (M = Nb, Ta; Z = Si, Cr, Fe, Co)
| Autor: | D. G. Naugle, Timothy Hughbanks, K. D. D. Rathnayaka, Kyungsoo Ahn |
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| Rok vydání: | 1994 |
| Předmět: |
Materials science
General Chemical Engineering Analytical chemistry General Chemistry Activation energy Atmospheric temperature range Conductivity chemistry.chemical_compound Metal halides chemistry Electrical resistivity and conductivity Materials Chemistry Ground state Electronic band structure Ternary operation |
| Zdroj: | Chemistry of Materials. 6:418-423 |
| ISSN: | 1520-5002 0897-4756 |
| Popis: | The resistivities of the rare-earth metal halides, R[sub 4]Br[sub 4]Os (R = Y, Er) and several of the ternary tellurides M[sub 4]Te[sub 4]Z (M = Nb, Z = Si, Fe, Co; M = Ta, Z = Si, Cr, Co) were measured using standard four-probe ac and dc techniques at temperatures ranging from 4.2 to 350 K. The rare-earth halides R[sub 4]Br[sub 4]Os show semiconducting behavior: conductivity increases exponentially with temperature. Activation energies (E[sub a]) for conduction in Y[sub 4]Br[sub 4]Os and Er[sub 4]Br[sub 4]Os are 0.16 and 0.11 eV, respectively. The resistivity of Er[sub 4]Br[sub 4]Os is 2 orders of magnitude smaller than that of Y[sub 4]Br[sub 4]Os at 273 K. The behavior of these compounds is in accord with the calculated band structure presented. The isoelectronic compounds M[sub 4]Te[sub 4]Si (M = Ta, Nb) behave as electronic conductors at high temperature. Ta[sub 4]Te[sub 4]Si shows a resistivity maximum at 160 K and below 60 K exhibits a broad metal-insulator transition. The absolute resistivity measured for Ta[sub 4]Te[sub 4]Si is 2 orders of magnitude higher than the other tellurides. The analogue Nb[sub 4]Te[sub 4]Si shows a similar anomalous resistivity maximum near 280 K and at low temperature ([approximately]60 K) exhibitsmore » a gradual rise in resistivity that suggests a semiconducting ground state. Transition-metal-centered M[sub 4]Te[sub 4]Z compounds all behave as simple metals in the temperature range 4.2-300 K; metal-insulator transitions are not seen at temperatures greater than 4.2 K. Nb[sub 4]Te[sub 4]Fe shows a small resistivity anomaly near 25 K. 30 refs., 10 figs., 2 tabs.« less |
| Databáze: | OpenAIRE |
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