Electrical conduction of new compounds (Ca,Ce)[sub 2]Sn[sub 2]O[sub 7] and (Sr,Ce)[sub 2]Sn[sub 2]O[sub 7] with pyrochlore structure

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1993.1044· OSTI ID:6515796

Wakiya, Naoki; Nishiyama, Shin; Shinozaki, Kazuo; Mizutani, Nobuyasu ^[1]

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1. Tokyo Inst. of Technology (Japan)

The electrical properties of sintered specimens of new compounds Ca[sub 2x]Ce[sub 2[minus]2x]Sn[sub 2]O[sub 7] (0.35 [le] x [le] 0.43) and Sr[sub 0.7]Ce[sub 1.3]Sn[sub 2]O[sub 7] with cubic pyrochlore structure were measured as functions of temperature and oxygen partial pressure. These compounds showed semiconductive behavior. The negative Seebeck coefficient indicates these compounds to be n-type, and the dominant carrier is the electron. In these compounds, almost no oxygen nonstoichiometry was detected in the range of oxygen partial pressure (pO[sub 2]) from 1 to 10[sup [minus]3.5] atm with thermogravimetric analysis. Moreover, the electrical conductivity slightly increased as pO[sub 2] decreased from 1 to 10[sup [minus]15] atm. Since it was required that part of the Ce ions should be trivalent to maintain the electrical neutrality in the whole crystal from the point of view of the chemical composition, the formation of the carriers was explained by the substitution of trivalent Ce ion for Ca. The Seebeck coefficient increased as temperature increased from 780 to 1,273 K, so the conduction mechanism of these new compounds is probably small polaron hopping. 16 refs., 4 figs.

• OSTI ID: 6515796
• Journal Information: Journal of Solid State Chemistry; (United States), Vol. 102:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM OXIDES
ELECTRIC CONDUCTIVITY
CERIUM OXIDES
STRONTIUM OXIDES
TIN OXIDES
CHEMICAL COMPOSITION
IONS
POLARONS
PRESSURE EFFECTS
SEEBECK EFFECT
SEMICONDUCTOR MATERIALS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 1000-4000 K
THERMAL GRAVIMETRIC ANALYSIS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CERIUM COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL ANALYSIS
ELECTRICAL PROPERTIES
GRAVIMETRIC ANALYSIS
MATERIALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUANTITATIVE CHEMICAL ANALYSIS
QUASI PARTICLES
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
TEMPERATURE RANGE
THERMAL ANALYSIS
TIN COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties