Polar-axis-deformation induced molecular pyroelectrics for waste heat harvesting

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14655
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 32020:Functional solid state chemistry-related
• Research Institution: Hokkaido University
• Principal Investigator: Huang Rui-Kang 北海道大学, 電子科学研究所, 助教 (60901296)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: Supramolecule / pyroelectricity / Structural flexibility / Thermal expansion

Outline of Final Research Achievements

Using 18-crown-6 (18C6) and 3-R-adamantane-1-aminium (HADA-R, R = H, F, Cl, Br, OH), a series of crystals were successfully synthesized. All of the (HADA-R)(18C6)ClO4 crystals contain similar 1D supramolecular columns structure. For R = H, both HADA-H and 18C6 are rotating above room temperature, while undergo rotational-freezing transitions around 253-333 K, resulting in the significant thermal expansions along polar axis as designed. For R = F, the HADA-F exhibit flipping motion in the 1D column with disordered NH3 and F at above 373 K, indicating the crystal may be ferroelectric at lower temperature. For R = Cl, the one-dimensional columns in the crystal were reverse-arranged so the polarity is canceled, and so does for R = Br. The R = Cl crystal showed negative-zero-positive thermal expansion associated with the rotation-swing-stationary transition of 18C6, whereas this transition was not observed in the R = Br crystal, which has a larger atomic radius.

Free Research Field

機能物性化学関連

Academic Significance and Societal Importance of the Research Achievements

This research would a) enrich the design strategy of functional molecular materials, b) expand the area of high-performance pyroelectrics, and c) enlighten the application of molecular materials in energy problems.