Novel strategy to prepare pure Cu4TiSe4 and its high-pressure Raman and thermoelectric performance investigation

Abstract

Low lattice thermal conductivity is crucial for enhancing the dimensionless figure of merit (zT), which is primarily responsible for determining the energy conversion efficiency of thermoelectric materials. Cu₄TiSe₄ exhibits ultra-low lattice thermal conductivity at room temperature. However, achieving a pure single phase has been challenging in prior research due to the high volatility of Se. This study presents a novel approach for obtaining single-phase Cu₄TiSe₄ through the use of Cu₂Se/TiSe₂ precursors coupled with spark plasma sintering. Phase purity and structure were confirmed by Rietveld XRD analysis and TEM. In high-pressure Raman studies a blue shift of the vibration mode towards high frequency was observed, and a pressure-induced transition of local structure occurred at ∼10 GPa. XPS analysis confirmed consistent chemical states between bulk and nanostructured Cu₄TiSe₄, indicating robust structural stability. Remarkably, bulk Cu₄TiSe₄ exhibits an ultra-low thermal conductivity of 0.1019 W m⁻¹ K⁻¹ at room temperature, while the nanostructured Cu₄TiSe₄ achieved a record-low value of 0.0503 W m⁻¹ K⁻¹. This work establishes a rapid synthesis method for high-purity polycrystalline single-phase Cu₄TiSe₄, providing a novel synthesis strategy and advancing the development of thermoelectric materials with low lattice thermal conductivity.