Ultrahigh piezoelectricity in (Ba,Ca)(Ti,Sn)O3 lead-free compounds with enormous domain wall contribution

The development of lead-free piezoelectric ceramics with high piezoelectric coefficient d ₃₃ is of great demand to replace lead-based counterparts. However, a plateau of the piezoelectricity has been reached over years for lead-free ceramics through traditional strategies of constructing phase boundary. Here, we introduce a new strategy in a ternary 0.818BaTiO ₃-(0.182-x)CaTiO ₃-xBaSnO ₃ system close to the rhombohedral side of the tetragonal-orthorhombic-rhombohedral phase boundary, where an ultrahigh d ₃₃ value up to ∼860 pC N ^{− 1}, higher than that of most lead-based piezoelectric ceramics and nearly all lead-free ceramics, can be realized at x = 0.108. Nonlinear dielectric and piezoelectric measurements, in-situ synchrotron x-ray diffraction and composition-dependent domain morphology evolution reveal significantly enhanced domain wall mobility after the composition substitution, contributing to almost ∼80% of the whole d ₃₃ value. Such a large piezoelectric coefficient together with a low piezoelectric hysteresis (8%) demonstrates good practical application potentials of high performance soft lead-free piezoelectric ceramics. The current study also provides a new paradigm for largely enhancing the piezoelectric coefficient of lead-free piezoelectric phase-boundary compositions.