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Author Forbes, Scott ♦ Yuan, Fang ♦ Kosuda, Kosuke ♦ Kolodiazhnyi, Taras ♦ Mozharivskyj, Yurij
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY ♦ INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ ANTIMONATES ♦ BISMUTH COMPOUNDS ♦ CALCIUM COMPOUNDS ♦ CHEMICAL PREPARATION ♦ CRYSTAL LATTICES ♦ DYSPROSIUM COMPOUNDS ♦ ELECTRIC CONDUCTIVITY ♦ ELECTRON CORRELATION ♦ ELECTRONIC STRUCTURE ♦ FERMI LEVEL ♦ GADOLINIUM COMPOUNDS ♦ PRASEODYMIUM COMPOUNDS ♦ SAMARIUM COMPOUNDS ♦ SEMICONDUCTOR MATERIALS ♦ SEMIMETALS ♦ TEMPERATURE RANGE 0400-1000 K
Abstract The Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases (RE=Pr, Sm, Gd, Dy; Pn=Sb, Bi) were successfully prepared from high temperature reactions at 1225–1300 °C. These phases maintain the same structure types as the parent RE{sub 9}Pn{sub 5}O{sub 5} phases, except for a Ca/RE mixing. The study and preparation of these phases was motivated by the desire to shift the metallic type properties of the parent RE{sub 9}Pn{sub 5}O{sub 5} phases to a level more suitable for thermoelectric applications. Electrical resistivity measurements performed on pure, bulk samples indicated all phases to be narrow band gap semiconductors or semimetals, supporting the charge balanced electron count of the Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} composition. Unfortunately, all samples are too electrically resistive for any potential usage as thermoelectrics. Electronic band structure calculations performed on idealized RE{sub 9}Pn{sub 5}O{sub 5} structures revealed the presence of a pseudogap at the Fermi level, which is consistent with the observed electrical resistivity and Seebeck coefficient behavior. - Graphical abstract: Ca substitution in RE{sub 9}Pn{sub 5}O{sub 5} leads to charge-balanced Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases with semiconducting or semimetallic properties. - Highlights: • The RE{sub 9}Pn{sub 5}O{sub 5} structure may be stabilized with calcium substitution in the form of Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5}. • The Ca{sub 2}RE{sub 7}Pn{sub 5}O{sub 5} phases maintain the parent P 4/n structure, albeit with Ca/RE mixing. • The Ca{sub 2}RE{sub 7}Sb{sub 5}O{sub 5} phases behave as semiconductors while Ca{sub 2}RE{sub 7}Bi{sub 5}O{sub 5} are semimetals with electron-electron correlations. • Electronic structure calculations yield a semimetal-like density of states for both Ca{sub 2}RE{sub 7}Sb{sub 5}O{sub 5} and Ca{sub 2}RE{sub 7}Bi{sub 5}O{sub 5}.
ISSN 00224596
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-10-15
Publisher Place United States
Journal Journal of Solid State Chemistry
Volume Number 242
Part 2


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