Oxide pyrochlores — A review

Subramanian, M. A.; Aravamudan, G.; Rao, G. V. Subba

doi:10.1016/0079-6786(83)90001-8

Cited by 2,526 publications

(1,893 citation statements)

References 189 publications

Supporting

Mentioning

1,776

Contrasting

Unclassified

Order By: Relevance

“…In the pyrochlore [3] structure however, apart from a few exceptions, lone-pair active A cations do not necessarily lead to polar, distorted ground states. Instead, pyrochlore compounds with lone-pair active A cations frequently accommodate the offcentering through incoherent, local displacements.…”

Section: Introductionmentioning

confidence: 99%

Displacive disorder in three high-k bismuth oxide pyrochlores

Melot

Rodriguez

Proffen

et al. 2006

Materials Research Bulletin

View full text Add to dashboard Cite

We use time-of-flight neutron powder diffraction to examine static displacive disorder in three different pyrochlore A 2 B 2 O 6 O 0 compounds with Bi on the A site. The compounds (Bi 1.5 Zn 0.5 )(Nb 1.5 Zn 0.5 )O 6 O 0 (BZN), (Bi 1.5 Zn 0.5 )(Ta 1.5 Zn 0.5 )O 6 O 0 (BZT), and (Bi 1.5 Zn 0.5 )(Sb 1.5 Zn 0.5 )O 6 O 0 (BZS), are of interest -particularly BZN -for their high dielectric constants in the absence of any phase transition from the cubic high temperature phase. The local structures of the three compounds is characterized by displacive disorder from the ideal pyrochlore positions for both the A and O 0 sites, with the precise nature of the disorder being quite similar. However the extent of displacive disorder is different, despite the B-O networks being nearly identical in the three compounds. The reported dielectric constants of the three compounds are related to the extent of local displacement, and BZN, with the largest extent of local atomic displacement of A and O 0 , is also reported to have the largest dielectric constant at 1 MHz. The dielectric constants are also related to the magnitudes of the thermal parameters of the different ions. The strongest correlation is found to involve the thermal parameter on the B site (Nb, Ta, or Sb). #

show abstract

Section: Introductionmentioning

confidence: 99%

Displacive disorder in three high-k bismuth oxide pyrochlores

Melot

Rodriguez

Proffen

et al. 2006

Materials Research Bulletin

View full text Add to dashboard Cite

show abstract

“…The relative stability of fluorite and pyrochlore structure types for a given composition is generally governed by cation radius ratio rules, r A /r B , with pyrochlore being stable in the region r A /r B = 1.46-1.78 [1]. For many years, Nd 2 Zr 2 O 7 (with a cation radius ratio of 1.54) has been known to adopt the pyrochlore structure when synthesised via a conventional solid state method.…”

Section: Introductionmentioning

confidence: 99%

“…Pyrochlores and fluorites display a variety of interesting properties, such as oxide ion conductivity, radiation stability, gas sensitivity, catalytic activity, superconductivity and giant magnetoresistivity [1][2][3][4][5][6][7]. In particular their potential as oxide ion conductors has led to the investigations of the fluorite-pyrochlore structural boundary, with the aim of correlating the degree of anion disorder to conductivity [2,8].…”

Section: Introductionmentioning

confidence: 99%

From fluorite to pyrochlore: Characterisation of local and average structure of neodymium zirconate, Nd2Zr2O7

Payne

Tucker

Evans

2013

Journal of Solid State Chemistry

View full text Add to dashboard Cite

NOTICE: this is the author's version of a work that was accepted for publication in Journal of solid state chemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in Journal of solid state chemistry, 255, 2013, 10.1016/j.jssc.2013.07.001 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe structural characterisation of Nd 2 Zr 2 O 7 prepared via a precursor route was performed using a combination of local and average structure probes (neutron total scattering, X-ray and neutron diffraction). We present the first total scattering and reverse Monte Carlo (RMC) modelling study of Nd 2 Zr 2 O 7 , which provides compelling evidence for the adoption of a disordered fluorite-type structure by Nd 2 Zr 2 O 7 prepared by a low-temperature precursor route.Annealing the material at high temperatures leads to a transformation to a pyrochlore-type structure; however, Rietveld refinement using powder neutron diffraction data shows that the oxygen sublattice retains a degree of disorder.

show abstract

“…The A-site is occupied by larger, trivalent and 8-coordinated cations, typically rare earth elements. The B cations are smaller, tetravalent and 6-coordinated, usually transition metals, i. a. Zr, Ti, Hf [1][2][3]. Therefore, there are a lot of possible combinations of chemical compositions for a pyrochlore-type of oxides, but the ordered structure occurs only for the ones in which the ratio of ionic radii r = r A /r B is in the range between 1,46 and 1,78.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

Stopyra¹,

Niemiec²,

Moskal³

2016

Archives of Metallurgy and Materials

View full text Add to dashboard Cite

A 2 B 2 O 7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho 2 Zr 2 O 7 and praseodymium zirconate Pr 2 Zr 2 O 7 via Polymerized-Complex Method (PCM). Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C) fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho 2 Zr 2 O 7 exhibits lower thermal diffusivity than Pr 2 Zr 2 O 7 . Additionally, PrHoZr 2 O 7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.

show abstract

Oxide pyrochlores — A review

Cited by 2,526 publications

References 189 publications

Displacive disorder in three high-k bismuth oxide pyrochlores

Displacive disorder in three high-k bismuth oxide pyrochlores

From fluorite to pyrochlore: Characterisation of local and average structure of neodymium zirconate, Nd2Zr2O7

Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

Contact Info

Product

Resources

About