Exploration of thermal conductivity switching material with periodic nano-structure transition

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K21075
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Katase Takayoshi 東京工業大学, 科学技術創成研究院, 准教授 (90648388)
• Project Period (FY): 2020-07-30 – 2022-03-31
• Keywords: 熱伝導率 / 構造転移 / 第一原理計算

Outline of Final Research Achievements

Large thermal conductivity (κ) modulation was demonstrated by the reversible 3-dimensional (3D) to 2D crystal structure transition in a nonequilibrium solid solution of (Pb1-xSnx)Se, where Pb2+ stabilizes a 3D cubic structure while Sn2+ does a 2D layered structure. The phase boundary of these phases was induced in (Pb0.5Sn0.5)Se bulk polycrystals by thermally quenching the high-temperature solid solution phase. Through the 3D-2D phase transition, the 1/2.9-times decrease of lattice κ was achieved by strong phonon scattering in the 2D layered structure, and the electronic κ was also decreased by 5 orders of magnitude due to the electronic phase transition from a 3D high conductivity state to a 2D semiconducting state. The total κ modulation ratio = 3.6 was attained at 373 K. The present strategy will lead to a novel concept for designing thermal management materials through crystal-structure dimensionality switch using nonequilibrium phase boundaries.

Free Research Field

材料科学

Academic Significance and Societal Importance of the Research Achievements

温度変化による層状化合物のナノ周期構造転移を利用して、熱伝導率が大きく変化する材料(Pb0.5Sn0.5)Seを開発した。実用化に向けては、相転移温度を向上させること、熱伝導率の昇温曲線と降温曲線のヒステリシスを小さくすることなど、解決すべき課題はあるが、さまざまな材料系や結晶構造系の固溶体に展開することでさらなる性能向上が期待できる。今回の研究で得られた、結晶構造を人為的に制御して熱伝導率を変化させるという全く新しいアプローチは今後、結晶構造や化学結合が異なるさまざまな無機結晶系においても、高度な熱制御が可能な材料開発につながると期待される。