Gigantic piezoelectricity in a polycrystalline ceramic actively maintained at a quadruple point

Transformative technologies demand polycrystalline piezoelectric ceramics with piezoelectric coefficients (<i>d</i>₃₃) exceeding 6000 picocoulomb per Newton (pC/N), but this goal has remained elusive because of the intrinsically weak nature of piezoelectricity and incomplete polarization alignment in polycrystals. We overcome this barrier by placing a polycrystalline lead zirconate titanate (PZT) ceramic in a temperature and electric-field control module so that it operates at a quadruple phase point (QP). This QP ceramic exhibited a <i>d</i>₃₃ of ~6850 pC/N, which surpasses that of commercial PZT ceramics by 10 to 30 times and commercial lead magnesium niobate-lead titanate single crystals by ~4 times. This exceptional property arises from the tricritical nature of the QP, a thermodynamic singularity that produces an ultrasoft lattice and enables complete polarization alignment in polycrystals. The module maintained this performance for surrounding ambient temperature ranging from 25° to 350°C.