The ZrW2O8 family of materials has been shown to exhibit the unusual property of negative thermal expansion over a wide temperature range α-ZrW2O8 itself shows negative thermal expansion from 2 K to 1443 K with a coefficient of thermal expansion α1 of -91×10-6 K-1 between 2 and 300 K This behaviour can be related to the unusual structure of these materials, which possess a family of low energy phonon modes with negative Gruneisen parameters α-ZrW2O8 also shows a phase transition at 448 K to β-ZrW2O8 in which oxygen atoms are dynamically disordered These phenomena have been investigated by a number of techniques Results of powder neutron diffraction at 260 different temperatures are presented

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Negative thermal expansion materials

Negative thermal expansion in magnetic materials

Temperature dependent magnetization of Ni0.5Co1.5MnSb quaternary Heusler alloy is investigated both theoretically (m-T) and experimentally (M-T). According to the XRD data, the crystal structure of Ni0.5Co1.5MnSb is compatible with the cubic crystal structure with space group symmetry Fm-3m and the lattice parameter of a = 5.968 A. Experimental M-T curve is obtained at H = 1 T. The Curie temperature is obtained at about TCEXP = 538.3 K. We also use effective field theory (EFT) developed by Kaneyoshi to model and investigate the m-T properties of Ni0.5Co1.5MnSb. We find that the theoretical m-T and experimental M-T results overlap at low temperatures (T   100 K). In particular, the theoretical mSb3-T curve of the central Sb3 atom is much closer to the experimental M-T curve of Ni0.5Co1.5MnSb than that of the other components (mMn1, mMn2, mMn3, mSb1, mSb2, mNi and mCo). Therefore, we strongly propose that one needs to pay close attention to the magnetization of the central atom especially in the lattice of Heusler alloys in both their predictive and experimental studies.

Key role of central antimony in magnetization of Ni0.5Co1.5MnSb quaternary Heusler alloy revealed by comparison between theory and experiment

Negative thermal expansion (NTE) behaviors in the materials with giant magnetocaloric effects (MCE) have been reviewed. Attentions are mainly focused on the hexagonal Ni2In-type MM'X compounds. Other MCE materials, such as La(Fe,Si)13, RCo2, and antiperovskite compounds are also simply introduced. The novel MCE and phase-transition-type NTE materials have similar physics origin though the applications are distinct. Spin-lattice coupling plays a key role for the both effect of NTE and giant MCE. Most of the giant MCE materials show abnormal lattice expansion owing to magnetic interactions, which provides a natural platform for exploring NTE materials. We anticipate that the present review can help finding more ways to regulate phase transition and dig novel NTE materials.

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Negative thermal expansion in the materials with giant magnetocaloric effect

Regulating the interfacial reaction of Sc2W3O12/AgCuTi composite filler by introducing a carbon barrier layer

Design of negative/nearly zero thermal expansion behavior over a wide temperature range by multi-phase composite

Fe-doped MnNiGe alloys were successfully synthesized by solid-state reaction. Giant negative thermal expansion (NTE) behaviors with the coefficients of thermal expansion (CTE) of -285.23 × 10-6 K-1 (192-305 K) and -1167.09 × 10-6 K-1 (246-305 K) have been obtained in Mn0.90Fe0.10NiGe and MnNi0.90Fe0.10Ge, respectively. Furthermore, these materials were combined with Cu in order to control the NTE properties. The results indicate that the absolute value of CTE gradually decreases with increasing Cu contents. In Mn0.92Fe0.08NiGe/x%Cu, the CTE gradually changes from -64.92 × 10-6 K-1 (125-274 K) to -4.73 × 10-6 K-1 (173-229 K) with increasing value of x from 15 to 70. The magnetic measurements reveal that the NTE behaviors in this work are strongly correlated with the process of the magnetic phase transition and the introduction of Fe atoms could also change the spiral anti-ferromagnetic (s-AFM) state into ferromagnetic (FM) state at low temperature. Our study launches a new candidate for controlling thermal expansion properties of metal matrix materials which could have potential application in variable temperature environment.

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Xiuliang Yuan

Papers

Design of negative/nearly zero thermal expansion behavior over a wide temperature range by multi-phase composite

Negative Thermal Expansion over a Wide Temperature Range in Fe-Doped MnNiGe Composites.

Enhanced thermal stability of Mo film with low infrared emissivity by a TiN barrier layer

Controllable nearly zero thermal expansion behavior in Mn3Zn1−xCrxN (0 ≤ x ≤ 0.20) compounds

Effects of Ni substitution on magnetism and thermal expansion of antiperovskite Mn3Ga1-xNixN (0 ≤ x ≤ 1.0)