Switching Between Giant Positive and Negative Thermal Expansions of a YFe(CN)₆‐based Prussian Blue Analogue Induced by Guest Species

Abstract

The control of thermal expansion of solid compounds is intriguing but remains challenging. The effect of guests on the thermal expansion of open-framework structures was investigated. Notably, the presence of guest ions (K ) and molecules (H O) can substantially switch thermal expansion of YFe(CN) from negative (α =-33.67×10 K ) to positive (α =+42.72×10 K )-a range that covers the thermal expansion of most inorganic compounds. The mechanism of such substantial thermal expansion switching is revealed by joint studies with synchrotron X-ray diffraction, X-ray absorption fine structure, neutron powder diffraction, and density functional theory calculations. The presence of guest ions or molecules plays a critical damping effect on transverse vibrations, thus inhibiting negative thermal expansion. An effective method is demonstrated to control the thermal expansion in open-framework materials by adjusting the presence of guests.

Perovskite-related ReO3-type structures

“…178 In this way, a ZT of 1.6 was reported for a synthetic alloy of com- 182 The cavities are larger than those of the simple oxides and fluorides, so there is often solvent, typically water, by Goodwin et al, 100 which showed that by including an intercalant species the transverse vibrations are dampened and NTE is suppressed (Figure 6b). As a point of interest, this dampening of NTE via intercalation is also observed for a related (non-ReO 3 -type) porous rare earth cyanide compound, 184 and illustrates the similar structure-property relationship between the systems. (Figure 7) (a), a potential hydrogen storage material, which is attractive because it degrades to H 2 gas and solid YB 4 under 1-5 bar of partial hydrogen pressure (i.e.…”

Mechanisms and Materials for NTE

“…The inserted species within cavities in the structure are adjacent to the linkers and so reduce the amplitudes of their transverse vibrations. Redox insertion of only 6% Li into Fe-doped ScF 3 switches the TEC from negative to positive (Chen et al, 2017 ), and the same change is found when K + or H 2 O is inserted into the channels of the cyanide framework material YFe(CN) 6 (Gao et al, 2017 ).…”

Reversible switching between positive and negative thermal expansion in a metal–organic framework DUT-49

“…26 The switching between PTE and NTE in the Prussian blue analogue YFe(CN) 6 was recently reported by Chen and co-authors. 27 However, there are no reports on the switching between PTE and NTE for highly porous MOFs. Herein, we present the rst report for simultaneous positive and negative thermal expansion for the same MOF structure, under different conditions applied.…”