Resistivity, superconductivity, and order-disorder transformations in carbides and carbohydrides

Thesis/Dissertation · Wed Dec 31 23:00:00 EST 1980

OSTI ID:6237696

Dy, L C

The electron transport in transition-metal carbides was investigated with special attention to ordering effects in substoichiometric carbides and to the influence of hydrogenation. The superconducting transition temperatures of partially ordered Nb/sub 6/C/sub 5/ and hydrided NbC/sub x/ were decreased from those of the original specimens, disordered NbC /sub 83/ and NbC/sub x/, respectively. The normal state resistivity of Nb/sub 6/C/sub 5/ displayed the bulge in its temperature dependence characteristic of high T/sub c/ superconductors. Hydrided carbide specimens showed reduced resistivity values, a result attributed to the reduction of defect scattering as the carbon vacancies are filled with substitutional hydrogen ions. The effect of the order-disorder transformation NbC /sub 83/ = Nb/sub 6/C/sub 5/ at 1030/sup 0/C was to reduce defect scattering also, as the carbon vacancies became incorporated into the periodic potential of the ordered phase. New data on the normal state resistivity and superconducting transition of single crystal NbC /sub 98/ and TaC /sub 98/ are reported. Resistivity results for non-superconducting HfC /sub 97/ and WC crystals are also given.

• OSTI ID: 6237696
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
CARBIDES
CARBON COMPOUNDS
CHEMICAL REACTIONS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HYDROGENATION
NIOBIUM CARBIDES
NIOBIUM COMPOUNDS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE