Synthesis and Properties of the Negative Thermal Expansion Material Cubic ZrMo<sub>2</sub>O<sub>8</sub>

Lind, Cora; Wilkinson, Angus P.; Hu, Zhongbo; Short, S.; Jorgensen, J. D.

doi:10.1021/cm980438m

Cited by 179 publications

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“…For example, for many years, cubic ZrMo 2 O 8 could only be prepared via a precursor route, whilst solid state synthesis gave monoclinic ZrMo 2 O 8 below 400 o C and trigonal ZrMo 2 O 8 above this temperature [16]. However, recent work by Readman et al has shown that cubic ZrMo 2 O 8 can be synthesised from the oxides in seconds at high temperatures (1090-1130 o C) [17].…”

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

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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.

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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

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“…Besides oxide-based materials [1][2], anomalous thermal expansion behavior has been observed in molecular framework materials containing linear diatomic bridges such as the cyanide anions [3][4][5][6]. Recent X-ray diffraction measurements have shown [6] that the hexagonal materials, Ag 3 Co(CN) 6 and Ag 3 Fe(CN) 6 , exhibit exceptionally large ("colossal") positive thermal expansion (PTE) along the a direction (α a = +140 × 10 ) .…”

Section: Introductionmentioning

confidence: 99%

“…These thermal expansion coefficients are an order of magnitude larger than those observed in any other material. Even simple cyanides such as Zn(CN) 2 are reported [5] to have an isotropic NTE coefficient (α V = -51 × 10…”

Section: Introductionmentioning

confidence: 99%

“…However, when Zn is substituted by Ni, a layered compound, Ni(CN) 2 , is produced [3] which has NTE in two dimensions (α a = −7 × 10 It has been proposed from pair distribution function (PDF) analysis of the structural data collected using high energy X-rays that NTE in Zn(CN) 2 is induced by an average increase of the transverse thermal amplitude of the motion of bridging C/N atoms, away from the body diagonal [7].…”

Section: Introductionmentioning

confidence: 99%

“…Further, investigation using ab-initio calculations [8] of the geometry and electronic structure of Zn(CN) 2 shows that the naturally stiff C≡N bond is paired with weak Zn-C/N bonds. This type of bonding allows large transverse thermally excited motions of the bridging C/N atoms to occur in (M-CN-M) bridges within metal-cyanide frameworks.…”

Section: Introductionmentioning

confidence: 99%

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Relationship between phonons and thermal expansion in Zn(CN)2and Ni(CN)2from inelastic neutron scattering andab initiocalculations

et al. 2011

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). We have measured the temperature dependence of phonon spectra in these compounds and analyzed them using ab-initio calculations. The spectra of the two compounds show large differences that cannot be explained by simple mass renormalization of the modes involving Zn (65.38 amu) and Ni (58.69 amu) atoms. This reflects the fact that the structure and bonding are quite different in the two compounds. The calculated pressure dependence of the phonon modes and of the thermal expansion coefficient, α V , are used to understand the anomalous behavior in these compounds. Our ab-initio calculations indicate that it is the low-energy rotational modes in Zn(CN) 2 , which are shifted to higher energies in Ni(CN) 2 , that are responsible for the large negative thermal expansion. The measured temperature dependence of the phonon spectra has been used to estimate the total anharmonicity of both compounds. For Zn(CN) 2 , the temperature-dependent measurements (total anharmonicity), along with our previously reported pressure dependence of the phonon spectra (quasiharmonic), is used to separate the explicit temperature effect at constant volume (intrinsic anharmonicity).

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Thermoresponsive Inorganic Materials

Evans

2002

Encyclopedia of Smart Materials

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The effect of temperature on the vast majority of materials is well known—as materials are heated, they initially expand in volume before eventually melting, subliming, or decomposing. Thermal expansion is often viewed as a deleterious property. Thermal expansion can, however, also be put to good use. It has long been known that the walls of bowed buildings can be pulled back into shape by a cooling iron bar; steel tires can be shrink‐fitted onto the wheels of railway carriages. Although these examples represent a technologically useful response to the stimulus of increased (or decreased) temperature, they do not quite fall into the category of “smart.” However, the very simple concept of coupling together two materials, one that has a large and one a smaller coefficient of thermal expansion to produce a bimetallic strip can certainly be considered to create a smart composite body. Here, the strains induced by the higher expansion of one material cause the strip to bend as temperature is increased, leading to a simple temperature‐sensing/responsive device. The vast majority of materials known and used in technological applications have a positive coefficient of thermal expansion; the reasons for this behavior are discussed. Certain materials, however, display the opposite property and contract in volume when heated. These materials thus have a negative coefficient of thermal expansion, which has led to their somewhat confusing description as “negative thermal expansion” (NTE) materials. The properties of these materials and the origin of these effects form the main topic of this article. Materials that have this unusual thermoresponse have a number of important technological applications. Applications related to specific materials are discussed. The first major area of application is in producing composite bodies. By mixing normal materials with a negative thermal expansion phase, one can achieve a composite that has a precisely controlled positive, negative, or even zero coefficient of expansion. Second, certain of the materials discussed can be chemically doped to control their expansion properties. Thus, one can envisage a single material that could be adjusted to have zero overall expansion. Such materials are of use where repeated thermal shock might lead to mechanical failure (an everyday example is oven‐to‐table cookware) or in optical devices such as high precision mirrors where any thermal expansion might distort optical properties. Materials that have strong intrinsic thermal contraction are most likely to be used as compensators for the positive expansion of other phases. In “negative thermal expansion” materials considered in the remainder of this article, there will always be an underlying expansive component caused by vibrational modes that tend to increase bond distances. In certain circumstances, however, these modes may be dominated by other more exotic effects.

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Synthesis and Properties of the Negative Thermal Expansion Material Cubic ZrMo₂O₈

Cited by 179 publications

References 20 publications

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

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

Relationship between phonons and thermal expansion in Zn(CN)2and Ni(CN)2from inelastic neutron scattering andab initiocalculations

Thermoresponsive Inorganic Materials

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Synthesis and Properties of the Negative Thermal Expansion Material Cubic ZrMo2O8

Cited by 179 publications

References 20 publications

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

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

Relationship between phonons and thermal expansion in Zn(CN)2and Ni(CN)2from inelastic neutron scattering andab initiocalculations

Thermoresponsive Inorganic Materials

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Synthesis and Properties of the Negative Thermal Expansion Material Cubic ZrMo₂O₈