Anisotropic strain-modulated monoclinic phases with giant piezoelectricity in high-index-oriented PbTiO₃ films

By combining phase-field simulations and first-principles calculations, we proposed to modulate the monoclinic phases of high-index-oriented PbTiO3 films through epitaxial anisotropic strain to obtain superior piezoelectric performance. It was found that the piezoelectric coefficients e(22) were remarkably enhanced (up to 2400%) in both (111)- and (110)-oriented PbTiO3 films. The excellent piezoelectric property is mainly attributed to the polarization rotation due to the flatter energy landscapes in the monoclinic phases, while the variation of polarization magnitude contributes little to piezoelectricity. Our research suggests modulating material properties through anisotropic strain, which might bring some insight to other functional materials.