Electrical properties of the square-antiprismatic chain compounds M[sub 4]Br[sub 4]Os (M = Y, Er) and M[sub 4]Te[sub 4]Z (M = Nb, Ta; Z = Si, Cr, Fe, Co)
- Texas A M Univ., College Station, TX (United States)
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) exhibits 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.
- OSTI ID:
- 7070726
- Journal Information:
- Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 6:4; ISSN CMATEX; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360606* -- Other Materials-- Physical Properties-- (1992-)
ACTIVATION ENERGY
BAND THEORY
BROMIDES
BROMINE COMPOUNDS
CHALCOGENIDES
CHROMIUM COMPOUNDS
COBALT COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ENERGY
ERBIUM COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IRON COMPOUNDS
NIOBIUM COMPOUNDS
NIOBIUM TELLURIDES
OSMIUM COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
REFRACTORY METAL COMPOUNDS
SILICON COMPOUNDS
TANTALUM COMPOUNDS
TANTALUM TELLURIDES
TELLURIDES
TELLURIUM COMPOUNDS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS