Achieving Temperature‐Insensitive High Piezoelectricity by Reentrant Relaxor Transition

Although precision sensors and actuators demand piezoelectric materials with temperature-insensitive high piezoelectricity (d₃₃), achieving such a property is physically challenging because high d₃₃ relies on tuning the material to the vicinity of a ferroelectric-ferroelectric transition but it renders the property highly temperature-sensitive. This issue is particularly prominent for lead-free materials. Herein, a lead-free Bi-doped (Ba,Ca)(Zr,Ti)TiO₃ ceramic showing a low-temperature reentrant relaxor transition is designed, which is a diffuse transition from a tetragonal ferroelectric to a reentrant relaxor, the latter characterized by orthorhombic (O) polar nanodomains embedded in the tetragonal (T) ferroelectric matrix. The reentrant relaxor composition exhibits a remarkable temperature-insensitive high d₃₃ of ≈350 pC N^-1 over a wide temperature range from -40 to 85 °C. In situ microscopic observations and phase field simulations reveal that the temperature-insensitive high d₃₃ in the reentrant relaxor composition originates from the synergistic effect between the reduction in the kinetic energy of the T-symmetric ferroelectric domains and the increase in the volume fraction of the O-symmetric nanodomains during cooling. This work provides a new recipe for designing lead-free materials with temperature-insensitive high piezoelectricity.