Tunable thermal expansion and magnetism in Zr-doped ScF3

Abstract

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc1−xZrx)F3+δ over a wide temperature and CTE range (αl = −4.0 to+ 16.8 × 10−6 K−1, 298–648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (αl = 2.6 × 10−7 K−1, 298–648 K) has been observed in the composition of (Sc0.8Zr0.2)F3+δ. The controllable thermal expansion in (Sc1−xZrx)F3+δ is correlated to the local structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc0.8Zr0.2)F3+δ at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials.

Controlling the Phase Behavior of Low and Negative Thermal Expansion ReO3-Type Fluorides using Interstitial Anions: Sc1–xZrxF3+x

“…Powder diffraction data recorded at beamline 11-IDB (Figure 1) show that all the Sc 1−x Zr x F 3+x samples (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were single phase cubic (Pm3̅ m) at room temperature, in agreement with a prior study of this system. 18 Over this composition range, the observed lattice constant decreases with increasing zirconium content (inset Figure 1) but to a lesser extent than previously reported. 18 It may be significant that the samples for the present study were prepared in a somewhat different fashion from those of Wang et al, 18 as it is known that the thermal history of fluoride excess ReO 3 -type materials can change their lattice constants.…”

Perovskite-related ReO3-type structures

“…This tuning can also be achieved by Zr doping. 98 It has also been found that NTE in ScF 3 can be essentially turned off by doping with a small amount of Fe and intercalating an equal amount of Li into the vacant A-sites. 99 The inclusion of Li ions limits the transverse vibrations of the fluoride ions, much the same way that guest molecules can dampen NTE in other porous NTE materials.…”

Tuning Thermal Expansion in Metal–Organic Frameworks Using a Mixed Linker Solid Solution Approach

“…Although most materials display positive thermal expansion (PTE) due to the inherent anharmonicity of bond potentials, − some display the anomalous properties of negative thermal expansion (NTE) or near-zero thermal expansion (ZTE). − In principle, NTE materials can be used to compensate for the PTE of a matrix resulting in a controlled thermal expansion composite. , NTE in open framework materials, , such as metal oxides, − ,, metal fluorides/oxyfluorides, − cyanides, − and metal–organic frameworks (MOFs), − typically arises from the presence of low frequency vibrational modes that soften on volume reduction. , Strategies for controlling NTE in a given framework, such as the formation of solid solutions or the insertion of guest molecules, ,− can be thought of as methods for modifying the vibrational modes and their response to volume change.…”