Metal-Semiconductor Transition in Tl2Ru2O7

Structural and Bonding Trends in Ruthenium Pyrochlores

“…tion from iterant to localized behavior (11)(12)(13). This raises the question of what the electronic implications of these in the Tl and Bi cation relative to the more normal semicon-atic since the lattice parameter has apparently contracted while the ''effective'' oxidation state of the Bi has deductors.…”

“…e.g., Y 2 Ru 2 O 7 . While there have been a number of atDuring the past 15 years there has been considerable tempts to correlate the structural and electronic properties growth in the number of reported studies on pyrochlore-of the ruthenate pyrochlores (3)(4)(5)(11)(12)(13) only for a handtype oxides as a consequence of the stability and diverse ful of these materials are precise structural data available. physical properties of these materials.…”

“…ponents in thick film resistors (10), and their unusual electronic properties (11)(12)(13); the Ru 4d electrons are The pyrochlore structure was first determined by von borderline between localized and itinerant behavior and Gaertner in 1930 (1) and over the following 65 years many depending on the A-type cation the materials are either hundreds of pyrochlore type materials have been charac-metallic Pauli paramagnets, e.g., Bi 2 Ru 2 O 7Ϫy , or semiconterized. Most of the earlier studies were the topic of a ductors with a spontaneous ruthenium atomic moment, comprehensive review by Subramanian et al in 1983 (2).…”

Bi2–xCaxIr2O6+y Pyrochlore Phases: Structure and Properties with Varied Ir Oxidation State from 3.9+ to 4.3+

“…Compounds with the pyrochlore structure (Figure ) have been studied due to the many interesting properties that have been observed for materials in this family. Abrupt metal–insulator transitions have been found for Cd 2 Os 2 ­O 7 (second-order) and Tl 2 Ru 2 ­O 7 (first-order). − Superconductivity occurs in Cd 2 Re 2 ­O 7 , and colossal magnetoresistance is seen in Tl 2 Mn 2 O 7 . − The magnetic properties of pyrochlores have been of considerable interest because of the frustrated magnetic interaction of M cations (Figure ). , …”

Structural and Electronic Properties of the Ru Pyrochlores Bi2-yYbyRu2O7-δ

“…Ruthenium pyrochlores of the type A 2 Ru 2 O 7 - δ have been widely studied for many years because of both their potential technological importance and their unusual electronic properties. − When the A-type cation is a rare earth ion they are magnetic semiconductors, but metallic conductivity is observed when the A-type cation is an ion with a 6s 2 outer shell configuration such as Tl + , Pb 2+ , or Bi 3+ . The ruthenium 4d electrons are on the borderline between localized and itinerant behavior.…”