B.T. Matthias

Rare-Earth Oxides of Manganese and Cobalt Rival Platinum for the Treatment of Carbon Monoxide in Auto Exhaust

The perovskite-like compounds RE1-XPb5MnO3 and RECoO3, where RE (rare earth) is lanthanum, praseodymium, or neodymium, are active catalysts for the oxidation of carbon monoxide. Crushed single crystals of these compounds compare favorably with commercial platinum catalysts in initial activity and lifetime. Therefore, these compounds are promising substitutes for platinum in devices for the catalytic treatment of auto exhaust.

Superconductivity of ternary sulfides and the structure of PbMo6S8

The compound Pb0.92Mo6S7.5, a derivation from the ideal stoichiometric compound PbMo6S8, is a member of the ternary sulfide series MXMo3S4 where M = Ag, Sn, Ca, Sr, Pb, Ba, Cd, Zn, Mg, Cu, Mn, Cr, Fe, Co, Ni, Li, Na, Sc, and Y. Members of the series with M = Pb, Sn, Ag, Cu, Zn, Mg, Cd, Sc and Y have been found to be superconducting at TC = 15.2, 14.2, 9.1, 10.9, 3.6, 3.5, 3.5, 3.6 and 3.0oK respectively. The lead compound has rhombohedral symmetry R3, lattice parameters a = 6.551A and α = 89.33°, and one formula per unit cell. The structure consists of a distorted primitive-cubic network of sulfur atoms with every fourth sulfur cube occupied by either a Pb atom or a Mo6 octahedron. The vertices of the Mo6 octahedron lie in the face centers of the sulfur cube which is tilted approximately 15o with respect to the rhombohedral axes. This arrangement yields open channels running through the structure parallel to the unit cell edges.

Upper critical fields of high-temperature superconducting Nb1−y(Al1−xGex)y and Nb3Al: Measurements of Hc2 > 400 kG at 4.2°K

Abstract Pulsed field measurements of the upper critical fields at 4.2°K, H c2 (4.2°K), in Nb 1− y (Al 1− x Ge x ) y and Nb 3 Al are approximately 410 kG and 295 kG respectively. The data are consistent with complete suppression of Pauli paramagnetic limiting.

Re-entrant superconductivity and magnetic ordering in the pseudoternary system (Er1−xHox)Rh4B4

Abstract The boundaries between the normal paramagnetic, superconducting, and normal magnetically-ordered phases in the tetragonal pseudo-ternary rare earth system (Er1−xHox)Rh4B4 have been established by means of ac susceptibility measurements to temperatures as low as 0.07 K.

Magnetic Ordering in the Rare-Earth Hexaborides

Magnetic ordering in the rare-earth hexaborides has been studied by a variety of methods, and a clear correlation with the presence of conduction electrons has been found.

Superconductivity in hexagonal tungsten bronzes

Abstract It is possible, by etching in various acids, to remove alkali-metal ions from hexagonal phase alkali tungsten bronzes, to change their lattice constants and to increase their superconducting transition temperatures substantially.

Superconductivity and electron concentration

Abstract Several systems are described in which the small additions of an element or compound lead to substantial changes of superconducting transition temperature. The conditions make it likely that the main effect is the change of electron concentration. In particular, molybdenum, reported to be a nonsuperconductor, is rendered superconducting by small percentages of rhodium.

The search for high‐temperature superconductors

Since 1911 superconductivity at room temperature has been the dream of scientists and science‐fiction writers alike. Unfortunately for superconductivity, the boundary between these two dream worlds has become totally blurred during the last decade. Still, today, superconductivity at room temperature together with controlled thermonuclear fusion are often mentioned as the two most important and crucial problems in physics relevant to the needs of society. Controlled fusion has now become a distinct possibility, and its progress over the last twenty years has covered many orders of magnitude. During this same time, superconducting transition temperatures have expanded from a range of 0.4 K to 16 K to a range stretching from 0.0002 K to 21 K. If this upper limit could be further increased, not by another order of magnitude, but by a factor of as little as 1.2, or as large as 1.5, superconductivity, while still far from room temperature, would revolutionize our technology. This revolution would encompass elec...

Clustering Hypothesis of Some High-Temperature Superconductors

Cluster formation in metallic crystal lattices is important for most high-temperature superconductors.

Superconductivity and structural behavior of hexagonal MoN and related Mo compounds

Abstract The results of high-pressure synthesis of hexagonal MoN are reported. Its transition temperature T c is in the range 14.8°–13°K. The high T c superconductivity is related to the presence of a superlattice, caused by clustering of Mo. The occurrence of Mo clustering in other superconducting or nonsuperconducting Mo compounds is discussed.