Synthesis and structural analysis of Bi{sub 2-y}Sr{sub y}Ir{sub 2}O{sub 7}, a new pyrochlore solid solution

Journal Article · Sun May 15 00:00:00 EDT 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.03.034· OSTI ID:21494268

Cosio-Castaneda, Carlos ^[1]; Mora, Pablo de la ^[2]; Tavizon, Gustavo ^[1]

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1. Departamento de Fisica y Quimica Teorica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico, D.F. 04510 (Mexico)
2. Departamento de Fisica, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico, D.F. 04510 (Mexico)

This paper presents a study of the synthesis and structural properties of the new pyrochlore-type Bi{sub 2-y}Sr{sub y}Ir{sub 2}O{sub 7} series. Ten compositions with 0.0{<=}y{<=}0.9 were prepared by solid-state reaction with thermal treatments at 873, 1073 and 1323 K under atmospheric pressure conditions. Structural refinements from X-ray powder diffraction data by the Rietveld method show that all compounds of the Bi{sub 2-y}Sr{sub y}Ir{sub 2}O{sub 7} solid solution crystallize in a {alpha}-pyrochlore structure. The main structural difference when bismuth is substituted by strontium concerns the x position of the O1 (x, (1/8), (1/8)). This substitution significantly increases the Bi/Sr-O1 distance and diminishes the Ir-O1 distance; this implies that the Ir-O1-Ir bond angle increases. With the Sr substitution, the IrO{sub 6} local configuration goes from a flattened trigonal antiprism, y<0.5, to an elongated one, y>0.5, passing through an octahedral array, y{approx}0.5. The electrical consequences of these structural changes observed in this system are qualitatively explained with electronic structure calculations, this behavior agrees very well with those observed in other pyrochlore systems A{sub 2}M{sub 2}O{sub 7} (A=rare earth cations or Tl{sup +}, Pb{sup 2+}, or Bi{sup 3+}, and M=Ru or Ir). -- Graphical abstract: Electrical behavior of the Bi{sub 2-y}Sr{sub y}Ir{sub 2}O{sub 7} solid solution. Display Omitted Highlights: {yields} Bi{sub 2-y}Sr{sub y}Ir{sub 2}O{sub 7} crystallizes in the {alpha}-pyrochlore structure. {yields} Local geometry of Ir goes from a flattened trigonal antiprism to an elongated one. {yields} Electrical resistivity increases with the Sr content in the solid solution. {yields} Electronic structure analysis relates resistivity with Sr disorder and bond strength.

• OSTI ID: 21494268
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 5; Other Information: DOI: 10.1016/j.jssc.2011.03.034; PII: S0022-4596(11)00131-9; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BISMUTH COMPOUNDS
BISMUTH IONS
BOND ANGLE
ELECTRIC CONDUCTIVITY
ELECTRONIC STRUCTURE
HEAT TREATMENTS
IRIDIUM
IRIDIUM COMPOUNDS
LEAD IONS
OXIDES
PYROCHLORE
SOLID SOLUTIONS
STRONTIUM COMPOUNDS
SYNTHESIS
TEMPERATURE RANGE 1000-4000 K
THALLIUM IONS
X-RAY DIFFRACTION
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
DIFFRACTION
DISPERSIONS
ELECTRICAL PROPERTIES
ELEMENTS
HOMOGENEOUS MIXTURES
IONS
METALS
MINERALS
MIXTURES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METALS
REFRACTORY METAL COMPOUNDS
REFRACTORY METALS
SCATTERING
SOLUTIONS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS