Enhanced piezoelectricity by phase transition in yttrium-doped carbon–boron clathrate ferroelectric

Carbon–boron clathrate ferroelectrics have emerged as promising candidates for high-performance piezoelectric applications. In this work, we investigate the origin of phase transition and the evolution of a shear piezoelectric constant in a Y-doped ScB3C3 system using first-principle calculations. The polarization in ScB3C3 is primarily driven by the off-center displacement of Sc atoms. Y doping leads to a reduced c/b ratio and induces a phase transition from the orthorhombic to the rhombohedral phase. This transition originates from the competition between long-range and short-range ferroelectric orders, where Y acts as a disruptor of long-range order, allowing short-range interactions to favor [111] polarization displacements. As the Y content increases, the shear elastic stiffness constant c55 gradually decreases, resulting in a large d15 near the doping-induced phase boundary. These findings demonstrate that the piezoelectric properties of carbon–boron clathrate ferroelectrics can be effectively tuned through ion doping, highlighting their strong potential for next-generation high-performance piezoelectric applications.