Q-factor measurements of the bulk resistivity and nonmetal-metal transitions in LaH/sub x/ and CeH/sub x/ (xgreater than or equal to2. 70)

Journal Article · Mon Feb 01 04:00:00 EST 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.37.2066· OSTI ID:5530798

Shinar, J; Dehner, B; Beaudry, B J; Peterson, D T

The resistivity rho(T) of CeH/sub x/, x = 2.70, 2.78, and LaH/sub x/, x = 2.70, 2.80 2.90, and 2.93, was measured in the temperature range 100less than or equal toTless than or equal to500 K, using an indirect Q-meter technique. The measured values of CeH/sub 2.78/ are in excellent agreement with the previous direct-contact measurements of Libowitz, Pack, and Binnie. In all cases except LaH/sub 2.93/, rho(T) peaks at 240less than or equal toTless than or equal to270 K, in rough agreement with the onset of the slight tetragonal distortion of the fcc phase and/or the formation of an ordered hydrogen superlattice. Thus, the temperature coefficient of the resistivity ..cap alpha.. is positive below the peak but negative above. In LaH/sub 2.90/ the peak is very sharp and the behavior semiconductinglike above 250 K. In LaH/sub 2.93/ the behavior is semiconductinglike throughout the measured range. The room-temperature resistivity of LaH/sub x/ rises sharply with x, from around 7 x 10/sup -4/ ..cap omega.. cm at x = 2.70 to around 0.5 ..cap omega.. cm at x = 2.93. These results are discussed in light of previous experimental results and band-structure calculations of LaH/sub 2/ and LaH/sub 3/. It is suggested that the peak in rho(T) is induced by an order-disorder transition, and the density of states at the Fermi level rapidly decreases to zero and a gap is consequently opened up as the concentration x approaches the trihydride stoichiometric limit.

• Research Organization: Ames LaboratoryU.S. Department of Education, Department of Physics and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5530798
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 37:4; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
CERIUM COMPOUNDS
CERIUM HYDRIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HIGH TEMPERATURE
HYDRIDES
HYDROGEN COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM HYDRIDES
LOW TEMPERATURE
MEDIUM TEMPERATURE
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
TEMPERATURE DEPENDENCE