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The negative thermal expansion (NTE) or nearly zero thermal expansion (NZTE) behaviors have been found in some magnetic metallic compounds with great application prospects. However, it is a big challenge for applications that the responding temperature range is not broad enough or far away from room temperature. Herein, a new method is put forward to design the wide temperature range of NTE and NZTE Behavior by NTE/NZTE multi-phase composite. In this method, the optimized volume fraction of the components achieves a concordant collaboration of multi-phase in the counteraction of NTE and positive thermal expansion (PTE) at several adjacent temperature ranges and thus the temperature range is broadened as expected. By this method, MnCuGeN-based NTE composite (290 K ≤ T ≤ 385 K, ΔT = 95 K) and MnCuZnSiGeN-based NZTE composite (200 K ≤ T ≤ 400 K, ΔT = 200 K) with excellent stability have been successfully designed and prepared. This idea will open an avenue to the multi-phase composite with designable NTE/NZTE properties, which would have important applications in aerospace and other modern industries.

Effects of Ni substitution on magnetic and thermal expansion properties in Mn 3 Ga 1−x Ni x N (0 ≤ x ≤ 1.0) were investigated. The magnetic structure for Mn 3 GaN is a typical noncollinear antiferromagnetic Γ 5 g . After Ni was introduced to the Ga site, the spin alignment was changed from antiferromagnetic to ferromagnetic. In addition, the magnetic transition temperature first decreased and then increased with increasing Ni content, which could be ascribed to the competition between the electron-type doping effect and the lattice effect. Near the magnetic transition, Mn 3 Ga 1−x Ni x N showed an abrupt lattice contraction with increasing temperature and the magnitude of the lattice contraction gradually decreased from 0.38% (for x = 0) to 0.09% (for x = 1.0) with increasing Ni substitution. In particular, zero thermal expansion behavior below 150 K was observed in Mn 3 Ga .6 Ni .4 N, and thermal expansion coefficient α was estimated to be 0.311 × 10 −6 K −1 . The obtained zero thermal expansion is very useful for practical applications in precision devices. The zero thermal expansion behavior was assumed to be associated with the ferromagnetic characteristic induced by the Ni substitution, which stabilized the Γ 5 g antiferromagnetic structure.

The antiperovskite Mn 3 Zn 0.77 Mn 0.19 N 0.94 was investigated by in situ neutron powder diffraction (NPD) in the temperature region 5–300 K. Here, a noncollinear-antiferromagnetic/collinear-ferrimagnetic phase separation (PS) showing different lattice parameters was firstly revealed in antiperovskites. The NPD results prove that the noncollinear antiferromagnetic phase, even coexisting with the collinear ferrimagnetic phase, could be responsible for the zero thermal expansion behavior of Mn 3 Zn 0.77 Mn 0.19 N 0.94 below 110 K. These findings suggest that Mn 3 ZnN based materials could open a new avenue for further exploring the noncollinear magnetic PS and correlated physical properties of antiperovskites.

The negative thermal expansion (NTE) and structural evolution of antiperovskite compounds Mn3Ga1−xGexN (0 ≤ x ≤ 1.0) were systematically investigated. Our results indicate the crystal structure of Mn3Ga1−xGexN changes from cubic (C) to tetragonal (T4) with increasing Ge content by X-ray diffraction (XRD).The negative thermal expansion from x = 0 (operation-temperature range ▵T = 20 K) to x = 0.4 (▵T = 60 K) becomes broad and shifts to higher temperature, and then it became positive from x = 0.5 in Mn3Ga1−xGexN. Typically, Mn3Ga0.5Ge0.5N shows low thermal expansion behavior between 300 and 450 K (∆T = 150 K), and thermal expansion coefficient α is estimated to be 2 × 10−6 K−1. Furthermore, variable temperature XRD was measured to reveal the origin of NTE. The cubic I - cubic II phases coexistence (x = 0.2) and cubic I - tetragonal coexistence (x = 0.5, 0.6) was observed at low temperature. The tunable NTE is highly valuable for practical applications in precision devices.

The fully dense, low-reacted Mn3Zn0.7Ge0.3N/Al composites were successfully fabricated by pressure infiltration technology. The large positive thermal expansion of Al is effectively suppressed by adding Mn3Zn0.7Ge0.3N component. Nearly zero thermal expansion (α=-0.41×10-6K-1) is achieved between 35 and 70°C in the composite with 30vol.% Mn3Zn0.7Ge0.3N. Moreover, the bending stress and modulus of Mn3Zn0.7Ge0.3N/Al composites increase gradually with increasing Mn3Zn0.7Ge0.3N content. This low thermal expansion, good mechanical properties materials is beneficial to electronic packaging and precision field.

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.

One of the specific subjects in frustrated magnetic systems is the phenomenon coupled with noncollinear magnetism, such as zero or negative thermal expansion (ZTE or NTE) in antiperovskite compounds. The first-principles calculations and neutron powder diffraction (NPD) are used to reveal the control of the noncollinear Γ5g antiferromagnetic (AFM) structure and corresponding thermal expansion properties in Mn3Zn0.875X0.125N (X = Mn, Ge, and Sn). Based on the optimal exchange-correlation functional, our results demonstrate that X (X = Mn, Ge, and Sn) doping at Zn site could stabilize the noncollinear Γ5g AFM structure and produce magnetovolume effect (MVE). The predictions of Γ5g AFM ground state and MVE is further verified by the NPD results of Mn3Zn0.83Mn0.15N0.99. Intriguingly, this special magnetic structure with strong spin–lattice coupling can be tunable to achieve ZTE behavior. On the basis of these results we suggest that frustrated magnetic systems with noncollinear Γ5g AFM structure of Mn atoms i...

We present the first-principles investigation of Sc1−xTixF3 (x ≤ 0.375). Controllable thermal expansion of Sc1−xTixF3 is achieved by different Ti contents. The negative thermal expansion (NTE) behavior is weakened gradually with increasing Ti content, which is consistent with experimental measurements. The Jahn–Teller effect plays an important role in the cubic-to-rhombohedral phase transition, which stems from the enhanced energy stability when the 3d orbitals of Ti3+ cation split into triply degenerate t2g and eg sets. The unusual thermal stiffening of Sc1−xTixF3 is found, which is similar to that of Sc1−xYxF3 and Sc1−xAlxF3 but contrary to other NTE materials.

In the past decades, the families of negative thermal expansion (NTE) materials have been in the uninterrupted growth with more new NTE materials reported; in particular, metal fluorides as the new members begin to draw attention. Herein, recent progress on the NTE properties of metal fluorides is reviewed, including compounds, mechanisms and the control of thermal expansion. Although some achievements have been made, there are still great development prospects. More in-depth investigations on metal fluorides with NTE behavior are expected.

The antiperovskite Mn3+xNi1–xN compounds have been synthesized and characterized by a variety of experimental techniques. After Mn doping at the Ni site, both ferromagnetic characteristics and an Invar-like effect were observed in the antiferromagnetic host material. The observed Invar-like behavior was assumed to be related to the characteristic magnetic structure induced by the doping. Neutron diffraction results prove that the Mn doping stabilizes the special Γ5g antiferromagnetic phase with strong spin–lattice coupling that can be tuned to achieve Invar-like behavior. The magnetovolume effect (MVE) and significant correlation between spin and lattice were confirmed for the Γ5g magnetic phase by the first-principles calculations. Moreover, Mn 3d electrons were revealed to be the key factor for the MVE from the calculations. Our study presents a new mechanism for precisely controlling the zero thermal expansion of a single compound by achieving the special Γ5g magnetic phase of Mn atoms.

An Mn3Cu0.5Ge0.5N/Cu composite was synthesized with 50 wt.% Cu and 50 wt.% Mn3Cu0.5Ge0.5N. The composite has a nearly zero thermal expansion behavior around room temperature and consists of Cu, Mn3Cu0.5Ge0.5N with a small number of MnO particles. There are no chemical reactions between these phases and the thermal expansion property of the composite is stable. Based on the distribution of Cu and Mn3Cu0.5Ge0.5N phases in the composite, we built a structure model to clarify the stability of Mn3Cu0.5Ge0.5N/Cu composite.

Mn3Zn0.7Ge0.3N/Al composites were successfully fabricated by pressure infiltration technology. The large positive thermal expansion of Al is suppressed by adding Mn3Zn0.7Ge0.3N component. Nearly zero thermal expansion is achieved in the composite with 30 vol.% Mn3Zn0.7Ge0.3N. Moreover, the bending stress and modulus of Mn3Zn0.7Ge0.3N/Al composites increase gradually with increasing Mn3Zn0.7Ge0.3N content. The low thermal expansion and good mechanical properties of these materials could be beneficial to the electronic packaging and precision fields.