Achieving High Performances of Ultra-Low Thermal Expansion and High Thermal Conductivity in 0.5PbTiO₃-0.5(Bi_0.9La_0.1)FeO₃@Cu Core-Shell Composite

Achieving high performances of ultra-low thermal expansion (ULTE) and high thermal conductivity remains challenging, due to the strong phonon/electron-lattice coupling in ULTE materials. In this study, the challenge has been solved via the construction of the core-shell structure in 0.5PbTiO₃-0.5(Bi_0.9La_0.1)FeO₃@Cu composites by the electroless plating, which can simultaneously combine the advantages of the negative thermal expansion material of 0.5PbTiO₃-0.5(Bi_0.9La_0.1)FeO₃ in controlling thermal expansion, and copper metal in high thermal conductivity. By changing the volume fraction of copper, the coefficient of thermal expansion of composites can be adjusted continuously from positive to negative. In particular, a ULTE (ΔT = 400 K) has been achieved in the composite of 35 vol % Cu. Intriguingly, a 3D thermal conductive network copper structure is formed for thermal conducting, which can double the thermal conductivity of the 35 vol % Cu composite from the methods by the traditional mixing (32 W·m^-1·K^-1) up to the core-shell structure (60 W·m^-1·K^-1). The present work not only provides a composite material with excellent comprehensive properties but also proposes a general chemical method to resolve the problem of low thermal conductivity in most ULTE materials.